Tip: Fire the ball on a place where you don't want it, then it will enter right where you want it to enter :D. Becouse it seems that's how the freaking suns work and i say why not holes too!
Packerlord, 1st of all yes after lvl 40, lvl 80. lvl 120 all creeps reset to sheep, rats (begining mobs) but they get more HP and Damage. Secondly why would you ever want to use "carry over" option ? If you lose go to title screen and load the last day u saved. Also, Bowgun mk-6 probably killed creeps in 2 shots only becouse they got stronger :/ OR when you had the bowgun mk-3 maybe it had damage mod lvl.3 or something so it was stronger then mk-6. Again hope this helps :P
Packerlord if you are stuck at a day and you say you are having trouble with all new levels i really suggest you start a new game with a Hunter (I play with this one, already on day 90 :P) or Rogue (many ppl say hes good coz he got loads of money). If you choose hunter just get a crossbow with like 3 or 4 slots for mods and keep upgrading it through the game (reforge). I hope this helps.