Warp weapons would use their explosive (hydrogen and anti hydrogen) as fuel, sustaining their warp travel. Basically when the weapon arrives at its target, there would be no fuel left to detonate. So for long range weapons it is unreliable and not really practical.

I like to think, he lived happily ever after, to the end of his days.

generally you're best to start where the actors are comfortable with their roles, and the show is developing in intensity and in a new direction, usually about season 4. Wrath of Khan, First Contact and Voyage Home are all great films to introduce the concepts.