1.Stats: Should Cofagrigus get a stat boost, Evolution, Mega Evolution or nothing?
Cofagrigus can get at most 57 BST.
Same goes for an evo.
A Mega would be possible with some boost.
2.Should Cofagrigus get more abilities?
YES. Cursed Body and Pressure are options.
3.Should Cofagrigus get more moves?
Recover can be an option.
4.What additional typing Cofagrigus can have?
Psychic, Dark, and Grass can be options.