Here's my thing on JimFor as much as people here dislike Jim, I have heard many many similar stories from people who have met them. Everyone always said that Jim was very lovely, friendly, kind and interested in whoever approached him/them (and leaving a very good impression) and that Tanya was basically a rude B. I'm not surprised you had the same experience. Has anyone ever had a good experience with Tanya? Because I have never read about it :S
He has never been cool or popular at school or whatever. He was the dorky nerd who was nice and quiet and didn't stand out. Definitely socially awkward, small group of friends and didn't like mixing and struggled making friends. But when you get to know him probably a decent enough bloke.
He seems to try to be nice to everyone he can, as people say, the stories are of Him being friendly and chatty, and Tanya being rude.
He's obviously grown more socially confident. But is still an awkward socially limited dork at heart so tries too hard to be nice and it comes across as trying too hard and weird.
He probably has also developed a liking for the attention the got as a popular YouTuber. Not the first, won't be the last.
Some of his childhood history probably plays a part of it, with an abusive father, he probably tries really hard to be the opposite of him, being overly nice at times.
Fundamentally, for all his flaws he isn't nasty, or mean. But probably struggles socially, and even him taking over as a dad from Sarah, probably comes from him trying to be nice, helpful and be a better Dad than his dad was. I can just be too much.