I think you sound like a great mom!! You are doing so many proactive things for your family!!
Kids don't like change, but guess what, life changes and they have to learn that the hard way. All we can do is offer comfort to them and try and talk to them about how they are feeling.
Her biting is in NO WAY okay, not at all, you are far more patient then I would be! :)
Be firm, be consistent, even if the punishment doesn't seem to be working, she knows how to break you and your hubby down.
DO NOT ALLOW HER TO RUN THE SHOW!
Put her in time out, period. If she gets up, walk her back.
Again and again and again, eventually she will realize she won't win this power struggle!
I have a strong willed little girl now 7 that I went through the same thing when she turned four. I just had to keep my sanity, which wasn't easy and stand tough. We went to play therapy to help communicate and it may or may not be something your daughter needs with the changes. It was a long road but we got there. Teaching her to control her outbursts, to realize there are consequences for bad behavior and put the control back to her on how her day goes. I learned to stop yelling, to listen more and to not react when she did. I set very clear guidelines of what I expected from her. Do not feel guilty about change though, they pick up on that and play off of it. You are doing an amazing job and she just needs to feel in control again.
Start the process with a firm warning, if she ignores you get on her level, walk her to time out, do not allow her near your arms and if she bites I am sorry but I would lightly tap her mouth and say "YOU DO NOT BITE ANYONE!!!" and have her face the wall! If she gets up just repeat.
It will be tough, not fun but around three and four I swear it is the hardest. I never had terrible twos with my kids but terrible threes and fours!!
Allow her choices to feel in control, when it makes sense, like clothes, what snack to have, give her option A and option B so she feels in control.
She is about power now and testing you, finding a way to adjust to changes and it is so important to carve out special time for her, really praise and rewardp positive behavior. JUST DO NOT TOLERATE meltdowns to the point she is hurting herself or others, tell her "I know you are upset however you do not act like that when you get your way, go to time out!" Give her a chance to go herself and then put here there if she doesn't.
I am a single mom and my kids went through some major changes and it did effect behaviors.I just stood my ground, gave them clear boundaries and stuck to my guns. They need some reassurance, security but also being consistent is key I found out! I can say being firm with mine at that age, they would go to the naughty corner by themselves and stay put, they tested me but didn't win. It certainly didn't happen overnight.
GOOD LUCK