1.Stats: Should Golisopod get a stat boost, Evolution, Mega Evolution or nothing?
Golisopod can get +10 BST at maximum.
An evolution with different stat distribution would be cool, but what Golisopod really needs is another Ability.
A Mega would work really well, given Golisopod's movepool.
2.Should Golisopod get more abilities?
YES. Entire reason Golisopod sucks is its Ability.
3.Should Golisopod get more moves?
Yes, more slashing moves and Fighting-type moves would be good, like Sky Uppercut, Psycho Cut etc.
4.What additional typing Golisopod can have?
Dark, Ground, and Ice are obvious options. Fighting and Rock are also options.