1.Stats: Should Basculin get a stat boost, Evolution, Mega Evolution or nothing?
A +15 BST update to match it to Bruxish would be decent at least.
An evolution is almost necessary for it to get any relevance.
Mega is unlikely, as it has an alternate form.
2.Should Basculin get more abilities?
Maybe. Basculin has good Abilities, but it would rather have moves to back its moves.
3.Should Basculin get more moves?
Probably. It has a very limited movepool, so it can get anything. Psychic Fangs and Hydro Pump are the most obvious options.
4.What additional typing Basculin can have?
Ice, Dark and Fighting are options. Rock is also an option.