Soo.. As for an update for this.
Avi has recovered from his timid behavior since Syfer was removed from the cage. It took some time, but he went back to his old self.
I kept them separated for awhile and would allow them to run around in this nice pen I bought them. They seemed to be fine in it, But Avi would be very cautious around the other.. Eventually allow him to be near him, even running over to him out of curiosity when he got into something. I thought things were finally progressing, till Syfer started chasing him in the pen. Avi didnt want to be near him anymore after that and would try to keep hidden from him.. I tried this again sometime later, but Syfer bit Avi, along with chased him.. So I went to giving them time alone, and let them run around in the pen one at a time, but keeping the pen by Avi's cage, so both could be in each other's presence. After some time of Avi getting over wanting to hide in his box again, he would become curious, watching Syfer from the bottom of the cage. Sometimes following him. I eventually allowed them to be close enough to sniff noses.. But then Syfer would try to bite Avi all the time, even attack the cage itself, so I no longer allowed that. I was rather discouraged at this point.
And then Syfer started destroying the dog kennel I had him in.. And I had no other option for delaying the situation any longer. I ended up putting him up for adoption. That was really depressing... But I wanted him to have a good, loving home.. with more space than I could offer him.
Avi seemed to be fine alone. In fact, he almost seemed happier. I rarely have seen him popcorn since he was younger, but he was running all over his pen, popcorning around, exploring everything. I was really happy to see this, and I let him out to play more often.
About 2 weeks later, I started noticing he wouldnt run to the top of his cage when I'd come home from work, and he started sleeping alot. He'd leave his box only to eat, drink, and pee.. He had no interest in toys anymore. But would run out when he heard the pen being brought out. And completely change and be super happy and play. O_o I did some reading, and from what I gathered, it sounded like he was depressed.. But his playtime attitude was throwing me off. When he was put back in his cage, he'd be normal and active.. Curious of whatever was going on around him. I even discovered that he loves my new scanner, and gets excited everytime I scan something.. It's funny to watch.
So, to try to distract him from being depressed, I'd keep giving him more attention, playtime, etc. He has improved alot since this.. But I cant help but feel really bad. I sometimes feel like I made the wrong decision giving Syfer up, but then get confused when I remember the reason why I had to because of his aggressive nature.. And then with Avi being depressed sometime after. Overall, I just feel terrible.
So I've been thinking of getting Avi a friend lately. A baby male buddy (weaned of course) as a better match for him, since he's so gentle natured. But I'm curious if there should be a waiting period before doing so.. Or would be it be a "sooner the better" situation. I was thinking the latter.. But have to wait till sometime in Feb, because I'm going out of town soon, and wanted to be around when the 2 adjusted to each other, etc.