#1
I could never figure out how to strum certain songs, so I would just play songs I can finger pick/pluck and all the songs I know are plucked or picked. is that bad?
#2
If I were you, I'd keep trying. Start with easier songs, and listen to the song a lot to get the rhythm and the groove.
You'll never learn if you don't keep trying.
#3
Bad? It's only "bad" if you want to be able to strum.

Good strumming technique come with time and a lot of practice. You need to be able to feel the rhythm and loosen up. If your arm is all tense, then you will always have problems. Most of the technique comes from the wrist, make sure your not bouncing your arm too much at your shoulder.

Good luck