Most of the seed banks have their own names for these strains, but look for anything with XXL in the name. Like Auto Pilot XXL. They are known for being heavy yielders and of course if you get autos, they will be finished in no time!
Can you post pics of your plants? In a 5 gallon your plants can be pretty decently sized before out growing the pot, but it really depends on height and how much training you've done. In a 5 gal I usually grow a 4-5 ft plant that is pretty bushy.
So it sounds like they got fried or burned from the miracle grow, which is a soil you should really avoid when growing cannabis. Full of harmful stuff! I'd say you're best to start over and do it right from the beginning as these problems will stay with the plant throughout the whole grow in...
Totally normal and not an issue at all. I'm guessing you have been misting them and when the water dries up that's left behind. It's usually just from the minerals left behind from the water.
If it's in veg then it will bounce back from any damage and be just fine. You don't need to change any thing, maybe prop up some of the damaged branches with stakes so they have some support but other than that you're fine. Try and harness that pot down so it doesn't fall over again as well...
You can grow in 100% perlite and it will work perfectly. Just remember you'll need to add nutrients and such if you go that route as it is an inert matter. I usually to a 50/50 mix of coco coir and perlite as the coir is a great medium to grow in and the perlite gives great aeration!