5th dnd – Do I have a disadvantage when I attack with a remote weapon?

This seems to be a houserule created by your DM. According to the rules, you do not have trouble with attacks with your weapon cleared from the hand, you do not add your ability modifier to the damage it inflicts. And, unless an exploit or ability says otherwise, the two weapons you use must be small arms, which limits the size of the weapons you can use with.

You may want to ask your DM why they introduced this extra rule or why they think that's the normal way to play.