new baker - wet sourdough-please help

Hi! so glad i found you! seems too good to be true!!!

i have had 6 good loaves, but this last set i thought wud be the best and instead it came out like a brick

i use Heckers unbleached AP

i proof in a 75 degree room

i let NYC water sit out overnite before i warm to 95 degrees to add to recipe

i use a good scale

my starter is very active and used it at peak

• 1 tablespoon 

  active sourdough starter

• 75 grams 

  all-purpose flour or bread flour (1/2 cup)

• 75 grams 

  water (1/3 cup)

• 525 grams 

  water (2 1/2 cups), divided

• 1 tablespoon 

  salt

• 700 grams 

  all-purpose flour or bread flour (5 1/2 cups)

with this recipe:  https://www.thekitchn.com/how-to-make-sourdough-bread-224367

its a Tartine-esque method I'm told

this time my dough tripled in size so i thought i was gonna have the  best bread ever!

i tweeked the above method per video by Chef Billy Parisi and let bread proof for 45 min between each S&F (instead of 30 min). It was wet but i cud l lift it and fold it over (i did extra folds thinking gluten formation is the reason for my small loaves) but when i put it on countertop to preshape, i had a puddle (it looked liked cookie dough on the counter)

I used a plastic scraper and with a lot of work I got some tension but it immediately melted.

I got some emergency advice and was told to add more flour and knead. So for one loaf, I continued to sprinkle in flour and used scraper to fold over and over. I couldn't touch it with my hands it was so sticky. This loaf cannot even by cut by a good knife! 

The other loaf I didn't score (more internet advice) and it is edible. its a lil gummy with ok oven spring on top half, with a very dense bottom layer of an inch.

Thanks so so much for advice!!!

Please lmk if I need to include any more info!!

Have a great day!!!