Today's Disaster

I'm trying to work on high hydration high whole wheat percentage straight doughs.  My previous attempt was OK, and I thought it would be better with a few tweaks.  Today's just spread out all over the peel after proofing.  

Kindly suggest places where I might have screwed up and what I could have done to fix it, if possible.

Formula:

Whole wheat flour (KA)   85%

High Gluten flour             15%

Water                              100%

Salt                                   2%

Instant yeast                      1%

Procedure:

1. Mixed flours (total 900 g) and 810 g water for a 30 min autolyse.  I keep the WW flour in the freezer, so I used hot tapwater.
2. Mixed in the remaining 90 g water + 18 g salt and 9 g instant yeast.  Mixed briefly in the stand mixer to incorporate, then did the first of 6 stretch and folds
3. Total of 6 stretch and folds; one every 20 minutes over 2 hours
4. Put the dough in the fridge.  In just a couple of hours in the fridge the volume doubled, so I degassed and did another stretch and fold.
5. Next morning, dough was pushing on the container lid.  When I opened the lid the dough dropped back by about 1/3.   
6. I divided the dough into 2.  Preshaping into rounds with a turn and tuck kinda sorta worked, but the dough was so soft that it didn't seem to tighten much.  I expect the worst at this point but continue just in case.
7. Rested for 3 hrs at room temp
8. Folded in some sauteed chiles and onions with stretch and fold
9. Tried to shape boules with tension-pulls but the dough was so soft that it wasn't getting much tension or shape.
10. Put each sort-of boule in a greased bowl for 3 hours.  I poked the dough with a wet finger and it bounced right back.  How could it be underproofed after 3 hours?  Would more proofing time have made any difference?  
11. Dumped the first bowl onto the peel and it spread like pancake batter

• Too much water for 85% whole wheat?  But the other 15% of high gluten flour also sucks up water.   I had intended 85% hydration but I must have had a late night brain lock-up when I wrote down the numbers.  
• Should I have mixed the dough in the mixer, 5 minutes on 1st speed, 5 minutes on 2nd with no stretch and folds  to build more gluten?
• Less yeast?  Cold tapwater?  Could it have overfermented? 
• Would more time resting or proofing have made a difference?
• Even before folding in the add-ins, the dough didn't seem really strong.  An 80% hydration dough supported some chopped olives pretty well.  But maybe 100% hydration can't support any extra weight?

Thanks

EDIT:  I baked the dough anyway.  The one that spread all over the baking stone actually had a nice open crumb, what I have been looking for, and a nice crust. And it tasted pretty good.   The only problem is that the loaf was one inch high.

The other loaf I stuck back in the fridge to proof for a while longer.  Then I baked it in a loaf pan.  I have not sliced it yet, but it did spring a bit and should be OK for sandwiches.