@Bottiger: 1: I just paid 2 refined for a level 77 huntsman. Levels can matter, it just depends on if somebody's looking.
@OP: I highly doubt anybody will look for a level 43, but you can always advertise in the SPUF levelled weapons thread.
2. Items used to be acquired solely through achievements - when the Sniper vs Spy update came out, the item drop system was introduced. Initially, weapons that dropped from that system could have non-standard levels, just like hats. It was later changed so that weapon drops could no longer have different levels. I'm not quite sure when it was changed, but I'm fairly certain that only items from the sniper/spy update and prior can be levelled.