You're little bumps are most likely dust particles.

I varnish in my garage. I used to wet the floor with a hose before varnishing.

Now I don't care. I have the garage door open and varnish. I've had bugs on it etc.
It still looks good after a fresh varnish job.

On a new boat I used to call it quits after two coats. I would do a 3rd at the end of the season especially if it was going to a wood boat gathering.