This is going to go the same way that everything else does with him adjusting to his new environment...SLOWLY! He's had a lot of new things going on recently, many changes, etc. And yes, as already stated, he needs to learn to feel comfortable in any room of the house, so the last thing you want to do is to keep him in one room most of the time, as that's exactly what will happen if you do that, he will end-up only feeling safe/comfortable in the office, and will start refusing to go anywhere else...But even when they end-up refusing to go into any other room of the house, what often happens is that you say "Okay, you stay in the office, I'm going into the living room", and then they end-up screaming their heads off as soon as you walk out of the office, so you come back and try to bring them into the living room with you, they refuse and freak out, go back into the office, but then again start screaming until you come back into the office...This is their way of training you!
So he simply needs time to warm-up to the new playstand and to spending time in the living room, kitchen, etc. He's obviously comfortable in the office, so now you need to work on the living room first, because that is where you spend most of your time when you're not working in the office. So I'd simply keep taking him into the living room when you're done with work...I would make sure that the playstand in the living room has lots of different toys on it for him, and I'd also start-out by playing with him on the playstand at first, show him that the playstand is safe, that it's fun, show him how to play with the toys/activities on it, etc. And just like anything else, it's all about exposure to it and time.
I think what you're going to find is that once your bond with him really becomes close and strong, which seems to already be happening and progressing, that he's going to get to the point where he just wants to be wherever you are at, no matter the room, and it's not going to matter where he's at, as long as he's with you. It's just not quite to that point yet, but you seem to be doing really, really well and things are moving actually a lot more quickly than they usually do. You're doing an awesome job with him and are providing him a great environment and loving home.
***Something you could try in order to make him comfortable with the new playstand, if it's easily mobile, is to move it into the office in the morning when you typically go to work with him. Since he is obviously comfortable with being in the office already, then sometimes that will also mean that anything that is inside of the office will also be safe and he'll be comfortable with it. So if it's physically possible, take a day or two (not long-term, but maybe for an entire 5-day work week at most, should do it if it's going to work), and move out whatever he's been spending time on/in in the office, whether it be a cage or a different stand, move that out of the office into the living room where he feels less comfortable, and then put the new play-stand that's in the living room into the office...So basically you're taking the cage/stand that he's comfortable with already because it's in the room he's comfortable with, and you're moving it into the room that he's not comfortable with in order to make the living room more comfortable, and then you're also taking the new play-stand that he's not comfortable with, probably because it's in the living room where he's not comfortable yet, and putting it in the office, where he is comfortable, and hopefully this will make the new play-stand okay...And continue having him in the comfortable office on the uncomfortable stand with you during the day, and then when you're done working you still want to move him from the office into the living room with you, but now he'll be in the uncomfortable living room but on the stand that is comfortable. The idea being that by the end of doing this for the whole week (possibly sooner, even right away, depends on the bird) he'll be comfortable in both room and on both stands, because you're purposely "blending" the comfortable and the uncomfortable together, along with you being in each room with him, and the end result will be him being comfortable with everything....
