Hi Mel
The COL night shift here!
We have all been there to some extent. Try not to worry.

Especially, don't panic. It is very hard to "spoil" a dog, and it is still early days anyway so you have loads of time to get back on track.
Firstly, keep on doing all the "right" things to stop him biting. It does work, but consistency and patience are essential.
However a major thing you do need to address is your brother and his behaviour in your home. You need to be very firm with him and let him know what is and is not acceptable behaviour towards Tali. Explain why and what you are doing to address the problems he can see (and may be contributing to!).
When Tali gets all manic, I would suggest playing with him for a while. But with your rules, not his. Then after a reasonable time, you call a halt to it all and start initiating some settling routines so that he gets the message.
It is great that he copes with the crate. Buddy never has, and only ever settled in it in our bedroom, with us. Not what we had planned!
Have you tried time-out? It's a long time ago, but we found a small, safe area for Buddy where he could do no harm to himself or to our property (our small hall was perfect. Don't use the crate!). Then when he got a bit out of hand we would say "time out" once. Then if he didn't respond we put him out in the hall. No fuss, no talking, just a pick up and out. After about 2 minutes, if he was quiet even for a second, we would get him back into the room. If he started up again we did exactly the same. At first it was a bit like a yo-yo, we didn't get to sit down for ages as he just played up so much. Sometimes we left him out there a bit longer. Up to about 5 minutes. But it's pointless trying to do longer than that. He did eventually get the idea. And before long, just the words were enough to get him to stop. I got into a bit of trouble on here, but we stuck a bit of wood over the door so that he didn't destroy it scratching to get back in. I didn't feel we could control that behaviour at the same time as working on the biting etc.
Don't beat yourself up. but do resolve to stick to a good training routine and stick to it. And DON't allow your brother to bully you.
(((HUGS)))