Don't apologise OP - just cos some people have less sleep than you, doesn't make your nights any easier. It's really tough with a little baby.
My DS did the same as your LO: 'sorted out' the first part of the night first, and like yours, started sleeping from about 8pm - 2am at around 2mo. He did gradually stretch that period of good sleep out later and later, but it was a good few months before he was settled from 4am onwards.
Tbh, I used to go the bed at 8pm as well, so I knew I would get a 5 hour+ stretch of sleep before the fun and games starts. I used to find that as long as I had a 4 hour block of sleep somewhere in the day I just felt like shit, as opposed to deranged/stumbling about/insane with exhaustion.
Also, what worked for us was a dream feed at around 10pm. So DS would have a bottle at 7pm and go to bed. Then I would go to bed. DH would stay up watching telly. Then at 10pm before he went to bed, he would gently lift DS out of his cot (keeping him in sleeping bag for minimal disruption), tickle his lip with a bottle, and he would drink the whole lot, pretty much still asleep. Then DH would sit him up and wind him, he would cry a little until a burp came up, then he would settle back to sleep on DH's shoulder before being returned to cot. DH then went to bed and I would deal wth all subsequent night wakings.