RE: I'm hoping I didn't make a mistake buying..
Im no expert, but about 10 grains per pound of arrow weight is good for bows in the 45 pound range. (45 pound bow = 450 grain arrow). A sharp 2 blade broadhead would probably be the best choice.45 pounds is plenty for deer, as long as you hit them in the right spot. So, as long as you are accurate with it, that bow will be fine. Also, for your first bow, 45 was probably the best choice, since there is no let off, that extra5 pounds is a pretty big jump.
This fall i'm using a 42 pound recurve with 500 grain arrows, because they flew the best. It is not fast as with a lighter arrow, but I don't doubt it will pass through a deer.
Good luck to ya.