First Sour Dough Loaf

First, try using a blend of bread flour and all-purpose flour (assuming you use a high protein flour). That will make the crust and crumb a bit more tender. You can also add a little bit (half a tablespoon) of olive oil to the dough to make it softer.

Second, I'm a fairly strong advocate of working the dough until it is stretchy and strong (meaning I think you're doing the right thing kneading to window pane). Some people feel differently, but I find if I underwork the dough the loaves tend to be flatter and more dense, because the gluten structure isn't strong enough to support a good rise.

Third, if it collapsed when you took it out of the bowl (assuming the bowl was where you did the final proof), it was probably overproofed. Where did it sit overnight? On the counter or in the fridge? If in the fridge, is the temperature 4C or warmer? At any rate, collapsing is a sign of overproofing, at which point it's not really salvageable. Try putting a small, golf-ball sized lump of the same dough into a straight sided shot glass or little measuring glass at the same time you shape the dough for the final proof. Watch and see how long it takes at room temperature to increase 1.5 times, or to double (probably a bit too much if doubled). The dough proofing in your bowl should be baked before it doubles (depending on what blend of flour you use; whole grains require less proofing and will over-proof more quickly).

I know, it's very confusing and you'll get all kinds of opinions, because people make bread in all kinds of different ways. Here's my take on the 'primer':

1. Mixing is when you mix up the starter, water, flour and other ingredients. The main variation at this stage is something called the autolyse, where you mix up some of the ingredients (usually just the flour and water but sometimes the flour, water and starter) and let it sit for a while (often around 30 minutes) to rest and absorb the water before proceeding. After you add the salt (and the starter, if not in the mix already) you should mix it until the dough is strong and stretchy. This can take 20 minutes by hand sometimes, or six to eight minutes in a stand mixer.
2. Bulk ferment - once the gluten is developed (i.e. the stretchy structure you got from mixing), you need to let the yeasts do their work, digesting the food in the dough and producing gases. This is what makes the dough increase in size and get lighter and more pouffy. The time and temperature for this stage varies a lot, and depends on things like how much starter you used and what kind(s) of flour. For a plain sourdough with 1 part starter, 2 parts water and 3 parts unbleached flour (all by weight, not volume), I will usually let it sit at room temperature for 4 to 5 hours until it shows strong signs of increasing size and lightness, then I'll put it in the fridge overnight where it will more or less stop fermenting and just develop flavour (the yeasts won't be active but the bacteria will be)
3. Shape - the fermented dough is manipulated to re-distribute the yeasts and their gases so it can rise again more evenly, without large pockets in some places and dense heavy dough in others. What a lot of people do is stretch the dough out gently, poking any big bubbles, then fold it in thirds (letter fold) or gather the edges into the middle (if forming a round loaf). Let it sit and relax for 20 minutes (this makes the dough easier to handle), then tighten the ball or 'log' into the final shape. There are a lot of different techniques for this, but the general idea is to form a tight shape without big bubbles trapped inside.
4. Proof - the shaped dough is allowed to rise again, now that the yeasts have access to more food. Opinions and techniques diverge here as to whether it's better to proof for a shorter period of time at room temperature, or a longer period of time in the fridge. This is the stage where you need to be careful because if the dough overproofs there's not much you can do about it, so I like to proof at room temperature and watch it carefully. The poke test is fairly reliable for a simple white sourdough - poke a floured finger or knuckle gently into the risen dough and see if the indent springs back. If it does, strongly and quickly, the dough is not ready to bake yet. If it doesn't spring back at all but the dent remains (or worse, the dough collapses), it is over-proofed. If it springs back partially and slowly it is probably good to go in the oven. If you proof overnight in the fridge and your fridge is not cold enough to completely stop the yeast action, you run the risk of it being over-proofed. I hate to get up in the middle of the night to check, myself, which is why I rarely use this method!

It sounds like you are almost there as far as your technique goes. Try the overnight bulk ferment and then shaping and doing the final proof at room temperature the next morning, just to see if that works for you. It will vary depending on the time of year (and how warm and/or humid your house it), and the recipe, but try it with a simple sourdough first and see how it goes. You can make changes after that, when you're more comfortable with the techniques.

Like most things, it depends. :) If I make a simple 1-2-3 sourdough (so, 100 grams of starter, 200 grams of water and 300 grams of mostly unbleached bread flour with 6 grams of salt), and retard it in the fridge overnight (part of the bulk ferment), I will usually take it out of the fridge in the morning, weigh it and pre-shape it, then let it rest for 20 minutes. After shaping and putting it in a basket or couche to proof I will usually let it do it's thing for around 2 hours before popping it in the oven.

Yes, as with everything in life it depends.  My SD recipe is a variation of David Snyder's San Joaquin SD that I have adapted to fit my own needs and taste.  My usual recipe is for two 500gm batards with a bulk fermentation in the refrigerator over night.  In the morning the dough is split into two equal portions, roughly shaped and allowed to sit on the counter for one hour.  After the dough has relaxed for this period of time, it is shaped into a batard and placed between the folds of a linen couche for 30 more minutes so it's at room temperature for 90 minutes total before going into the oven.  I always get a nice bloom in the oven and have not encountered any issues other than an occasional problem with my slash such that I get a on the side.  Oven temperature is 460F for 15 minutes with steam followed by 420F with no steam but convection.  Bread is baked on a steel.

Take out of the fridge and go straight into the oven without bringing up to room temp.

I've done it both ways, room temp, and cold with the same batch of dough to see if it made a difference. It didn't. The cold dough is much easier to score for one. 

The term "french loaf" can mean somewhat different things to different people. Even words like crispy and crusty are subject to personal interpretations; e.g. a loaf I consider moderately crusty might be very crusty to you. 

Have you made a yeasted loaf that fits what you want? If so, it shouldn't be difficult to convert the recipe to give you a similar SD one.