Please help me on how to start a starter!

I am very new to sourdough, as I have only made 2 loaves (1 Biga/poolish and one with a bit of starter from a friend).

I want to be able to make my own sourdough starter, but as of yet every single one of my starters either fails to double after two weeks of feeding every 12 hours or becomes so acidic (smells like ammonia, this smell usually starts within 4-5 days after I begin my starter) that it fails to rise at all.

I will try to be as thorough as I can in my explanations and how I do it.

This is how I usually make my starter:

120 grams bread flour (pilsbury)

120 grams water (tap, city water, room temp)

I use a glass quart mason jar and mix with a metal spoon.  My house it about 65-70 degrees F usually in the day and drops to 60F at night.

Twice a day, I discard down to 1/2 cup (60 grams) then add another 120 gram flour (1 cup) and 120 grams water (1/2 cup).  Mix it with a metal spoon, cover with plastic wrap with holes poked in the top, and set it near/in the sun of my window.

I've tried this about 5 times and every time my sourdough starter fails by about day 6: it always seems to acidify too much.  So now I'm ready to try again.  I have as of yet tried all wheat flour starter, half bread flour half wheat flour, and also gotten and used jugs of filtered (distilled) water and that has not improved my results.

I would love advice.  I recently bought rye pumpernickel flour and am wondering if that would help my results.  Someone else mentioned pineapple juice.  Are those good ideas?

It's so discouraging when I nurture something only to have it die, but I refuse to give up!  If you guys can all make great starters, so can I!  Thanks for all the help!

As an alternative, I could also buy a reputable (100 year old, 500 year old) sourdough starter off the internet and use that as my base to start my culture if that's easier for total beginners.  I really want to make true and honest sourdough bread.

(This is the website I use for making/nurturing my starter:) https://www.feastingathome.com/sourdough-starter/