This game is NOT an RPG. It is IMPOSSIBLE to rolepay

I have a serious, logical, practical, professional ryder who I made a little backstory for beyond what they say. He was in the military on earth for years. He is more like 27. He doesn't joke around with Liam at all. He feels like Liam is a poor fit for the team and he is generally very professional with him but tries to not come off like a dick. Sometimes he is more casual and maybe will crack a joke. He tries to keep things more relaxed as he rolls because he knows that with someone like Liam or some of the crew that might work better. But my Ryder is dead serious most of the time. He's got some years in the military before his dad reached out to him. He knows enough to take things seriously but he also knows that with some people in some situations, you kind of have to adapt a bit to who they are because they don't seem to function very well if you don't. 

As for how he responds in those cases of his past, I get what you are saying. For my Ryder, the more professional serious version I play, it is a mix of reason and without having a solid grey area where that could be articulated, he just decides what fits the moment best. Part of his reason was because he wanted to explore space, to be out there in the galaxy doing stuff but he was gimped by his dad's name because of the AI. So he has a mix of explore, get away and need a fresh start. He doesn't hate his dad. He understands WHY he did what he did, he just wished it didn't make him doing what he wanted to do such a problem (family name). But he loved his mom and also did want the AI to be able to save her. So he is the very definition of mixed emotions on that one. Coming to Andromeda gave him that fresh start he needed, but it was hugely due to him wanting to explore and be involved in things like the andromeda initiative, space exploration, meeting new races, and protecting people - helping them when he could. 

With Liam, he gets what Liam is all about very quickly (because over the years he has learned enough about people to size them up fast for the most part) and he just rolls with it realizing that Liam is a bit about to go off the deep end and if he doesn't take it down a bit in seriousness, Liam will probably lose his shit completely, which we pretty much see him almost doing later on in that whole mission (shooting the corpse endlessly). He also is a bit sarcastic at times as part of his personality. Like the weird alien machine commentary in their ship/base. He's out of his own depth here and he's got a bit of that in him but that is not how he is as a rule. It's just how he is occasionally. 

Maybe that will help you a little bit to try to have a character that works for you. I get where you are coming from because I had to find a way to adapt to it myself.