Stunted Growth, please help so i don't make mistake twice

Hi there, thank you for taking a look, I beg of you to be patient because I'm about to explain everything, hopefully you can help me figure out what I am doing wrong so I can have a smoother 2nd grow. 1st I'll describe my setup and mistakes I think I made, then I'll propose what the potential problems could be.
This is my very first grow and I am sure the growth has been stunted from 1 or more reasons. I will attach pictures as well.
Strain: 4 seeds, Ambrosia "Jordan of islands" or whatever, (bought in Canada/given to me, not my first choice but they were free )
Light: Germinated w/ paper towel, 75w Fluoro for first 2 weeks. (2.5-3" tall, good looking leaves). Changed over to new 400w HPS w/ a built in ballast. Put the height at 18" overnight w/ out a fan (big mistake) 2 seedlings died because I misted so much day before they fell over and bent their stem, didn't recover, two others were ok. SCHEDULE: 24/0 first 2 wks, 20/4 past 3.5 wks, 18/6 past 4 days.
**Currently in week 6 of veg stage and a whopping 6 inches.
Soil: Schultz African Violet potting soil Plus, even after a ton of research I was swayed into buying this 9 month time release soil because it had everything I was looking for, (perlite, sphagnum moss, composed materials, and for flowering plants it said!, seemed I hit the jackpot)
Environment/Closet: Terrible location but it is all I have. I have a walk in closet, which i tuck my plants (now plant) behind a dresser. Mylar covers 3 sides and a fan blows under and accross my 400w HPS. there is very poor ventilation because I can't do anything to wall/door. I leave for approx 5 hrs tues and 4 on thurs the heat builds up from 79-89 to 95-107. Humidity drops from 47-58% down to about 30-38% I mist average 1 time a day, ussually when i get back and they are hot.
**1 plant left
Containers: for the past 6 weeks of seedling/veg. stage they have been in 6" pots. it is now six inches and I transplanted it into a 12 inch 17 qt. pot. I noticed the roots on the bottom and they made markings on bottom of pot. Nothing like a root ball but a few hairy roots on bottom and sides. Because I decided to rip out the other teeny plant and I didn't want to replant my good one again to fit better in the center, it sits with the stem 4" from the side of the pot. Stupid to put them both in the same and then just remove one but I figured all hope was lost. Will being close to the side hurt the growth?
New Soil: In the new pot I added MG "Organic Choice potting mix", it is totally natural and completely unlike the original soil. I assume this is bad
Food: after the transplant last night, tonight I added more soil to fill up the pot and I gave it a drink of Schultz's 10-15-10 plant food plus. dose says 7 drops/1qt. water, I did, 2 drops/24oz. of water. We'll see how it looks tomorrow. I also moved it a bit out of direct light.

What I think could be the PROBLEMS:
This is what my research tells me what could be wrong, let me know what you think. Take a look at pics to see the yellowing/curled under and 1 set of hanging leaves.
1. Soil, time released is not the answer
2. pH looked to be 7ish when I started, maybe slightly higher
3. Nitrogen deficiency from root lock out caused by a pH?
4. Head stress, this is definitely a major reason I think
5. over ferted from time release
6. 6" plant in about 4-4.75" of soil (root bound maybe)
7. Poor soil breathing (3 holes, should I have removed the water collector to add 3 more holes?)

Thats everything I'm pretty sure. If you read all that I really do appreciate it and would LOVE some feedback.
Thanks!!!!!

shoot, I'm on my gf's comp and can't do the pics just yet. My mac harddrive just crashed and its will be a couple days.

Your on the right track with your thoughts on the cause man.
From my experience, these are my top tips for stunted plants:
- Fertilize - As directed with a good 2 or 3 part liquid nute for soil.
- Remove pot from plant to check roots, if there's alot of roots coiling around the inside of the pot, up-size it.
- PH - Yes you may be root locked. Go for a more acidic PH, I tend to aim for around 5.0-5.5


General:
Soil - use good crumbly soil with good aeration and water retention. The original perlite, sphagnum moss, composed materials soils sounds decent, but don't rely solely on the time release nutes.
Remove saucer - good soil should stay damp, you want good drainage and aeration.
PH - monitor and adjust
Strengthen plants - point a fan at your plant/s to strengthen them, stake later if needed.
C02 - boost growth by adding C02, search the forums, there's a few posts on it.


Hope this helps man, gl

107 degrees is WAY too hot for a seedling man.
I suggest using a much cooler lighting system like fluro's if you cant do anything to bring those temps down.
That way you'd have a smaller yeild, but your plants will be able to survive without having to worry about getting fried by the lights.

yeah my buddy who gave me the seeds started his like a week or two before me and hes got 400watts of those T5 lights, no ballast and no heat, his are 2.5-3 feet tall now and looking beautiful, my heat problem totally ruined my hopes for the extravagant HPS

Here is what my plant looks like at 6 weeks now

Anyone think it has a chance of being a female after all the stress it has gone through?? I'm still having trouble with humidity. 30-40% at 86 degrees ave. ranges from 78-90 i keep the closet door open now so thats the worst the temp gets now. before the temps were totally screwing with the growth. Please give me pointers!