1.Stats: Should Miltank get a stat boost, Evolution, Mega Evolution or nothing?
Miltank is basically inverse Tauros, but same things that have applied to Tauros apply to Miltank as well. It should get +50 BST regardless of how it gets it.
2.Should Miltank get more abilities?
In terms of abilities Miltank has, it is the same as Tauros, again. Its abilities are decent but not good by modern standards.
Contrary, Gluttony, Iron Fist and Cute Charm are all decent potential abilities for Miltank. Vital Spirit would also be cool.
3. Should Miltank get more moves?
Payback, Wild Charge, Hyper Voice, Uproar, Head Smash, Heavy Slam, Jump Kick, Megahorn, Screech and Supersonic would be all fitting moves for Miltank. Miltank would also enjoy some old moves for Level-Up like Power-Up Punch
4.What additional typing Miltank can have?
Fighting, Ground, Rock would be primarily fitting. Electric, Psychic, Steel and Ice would be lesser fitting types.