Yep, sounds like the old "territory" is gone and now there's a new pack member in the new territory (you). Baxter has likely decided that he needs to reestablish where he stands in the pack, and may be trying to move up to the number two spot below Alex, with you and the kitty as subordinate pack members.
For you: Look up "NILIF" (nothing in life is free) on Yahoo or Google. There are 20-30 articles on the topic but they pretty much say the same. It is a group of techniques to establish you as a pack leader, not a subordinate. Baxter needs to learn that he is below you in the pack order. You and Alex need to read the NILIF techniques and both be consistent in Baxter's learning. For now, do not allow him on the furniture or bed (wherever he trying to squeeze in) unless you have specifically invited him. Until he can come up without charging you, he's not allowed at all. Alex has to back you up.
For kitty: You may want to keep them in separate areas of the house unless you or Alex are supervising to break up any attacks until they again learn to peacefully co-exist again. (I take it they were getting along fine in the apartment?)
By the way, congratulations on the marriage!
