Is finn's father alive?

In the original universe, we've seen Finn's father, Martin in the episode "Escape from the Citadel". He then escaped to space, but he might have a chance of being still alive.
If you're looking for Farmworld Universe, Finn's father (Mr. Mertens) ran away with his family after Ice Finn told them to do so. Not sure if he's still alive.
Then after Jake's wish (In "Jake the Dog"), that universe was probably somehow altered. So who knows?

he could have entered the empty vacuum of puwang and died of lack of oxygen (as he sinabi at the end of the episode really fast as the entered the portal "hey what about oxygen?")

or he could have simply gone somewhere else ligtas as can be...

point being is we can't be sure until he resurfaces, dead or alive.

Yes if you've seen Finn The Human his dad in farmworld looks a bit like Adventure Time Dad

Yes he is but Finn's Father is a %$#@*&

Yes as we saw in "Escape the Citadel" he went off into space. But in "The Tower" we thought Finn's father was in the tower but it was just PB in disguise. So I'm not very sure if Martin is alive or not only time will tell.

For me. Yes, but not as we saw him. Because in stuff like Fionna and Cake they easily resemble the other version of them. But still it's a book