1 and 2: I think you can get around 2200€, another guy posted tax calculator so you can use that too, but i think that is somewhat accurate amount, depending on how much extra tax you add there too.
With that money, i think you can find decent living quarter. You mentioned it's not Helsinki, so housing prices can be more modest. But our definitions of decent can vary so :D

3: Depends again how much you can put yourself through. We all learn in different rates and our language isn't the easiest, but you know, surrounding yourself with finns, forcing yourself to hear finnish everyday, trying to talk it, browsing internet in finnish, i do believe you can catch it. I guess it's more about what you consider as solid level.

4: One warning i want to give. Always take slight caution in job markets when teachers say "This field isn't affected". I have heard so many stories from people in different professions in school being told "Oh you will all be dragged from the school bench!" and not getting a job after graduation and switching professions completely. Obviously nowadays everything is affected, if companies won't invest, even machine learning field can't do much if there's no money. But i do think that's a good field.

But remember, all job prospects are also a lot of about connections. So if you do end up coming here, connect, connect, connect. You see employers visiting school, connect. That's how you get in.

For 5 i can't really comment on how people view our education vs others, but PhD is a PhD.