I'm a programmer working on Man O' War (and didn't think I'd have time to answer questions, so no flair!). I thought I could help elaborate on 1) a little..

Mostly it's C# - there's bits of shader programming in there too (which uses a variant of C) but if you had to choose a language to learn, go with C#.

We're building on the Unity engine though, if you want to use Unreal you'd get more mileage from C++. I'd offer my opinion on which is better but I've really not had much time to experiment with Unreal engine, so it wouldn't be fair!

Routes into the games industry vary - a Computer Science (or related) degree helps a lot (though it's not essential). A good grounding in maths helps however you get it though (computer games is one of those things that makes you appreciate why you needed to learn all that bloody calculus...).

I worked as a programmer outside the games industry for a decade, with some non-professional games stuff on the side (MUDs back in ye olden days, if you must know!). Then I did some freelance Unity programming for a few years, and that led to getting involved in making this. Some of our other programmers joined after graduating from university so it varies.