Potty training...you might have to start from the beginning again and that means taking him out more often than once an hour, after meals, after naps, after play, etc. Reward and praise him each time he does it outside. If he does it inside, "no" and then take him out. Also, keep the leash on at all times and the other end tied to you if possible and you have to keep an eye on him constantly. Don't let him run loose inside until you're confident he's potty trained. If you live in a cold place, have the jacket, shoes, gloves, scarves, all in the same place and ready. Try to get into a regular schedule everyday. If you can't keep track of when he last pooped or when he peed, keep a log. I did (I still do). I wrote down the time when mine went to pee, eat, poop. It helps to better predict when he may go next, especially if your memory is not great or you have other things on your mind. Mine is now 6 months old and I only keep track of his pooping schedule. I keep track of how much he pooped, if it's diarrhea, etc. I do it just so I can estimate when he needs to go next and that way I can plan my own schedule, like what time I need to be back if I'm out eating lunch or grocery shopping or etc. Sometimes vets will ask you about your dog's poop. I can just pull up my notepad and tell the vet what he needs to know. I know writing it down is extra work, but it's work that helps me a lot.
The biting...I've said this many times before in other threads...there's no instant cure for the biting. You just have to power through it. I went through 2 tubes of Neosporin and 3 boxes of bandaids. The biting should decrease significantly when he's done teething. Mine still bites but he only bites when he needs to go out. When he starts biting my hands, then I know he has to pee or poop. That's his signal.
The crate/cage/pen...You made the mistake of letting him out when he started crying. So now he knows he can get what he wants when he cries. Buy ear plugs or listen to music with headphones on to lighten the sound to your ears. Buy a bottle of wine or pizza or something for your neighbors and explain to them. They may be more tolerant after that. Put him in the pen when you go to the bathroom, or get the mail, or eating dinner, or vacuuming or etc. Anytime you can't watch him...in the pen even if it's for 2 minutes. The more times he's in there and then gets let out, the more he'll understand being in the crate is ok. Give him treats when he's quiet in the crate. When he goes in, treat. If he cries, no treat.
I give you mad props for trying to do all this living in an apartment. I would never raise a pup living in an apartment, but that's just me. Anyway, good luck.