Toilet Flange - Will this work?

I just installed a toilet flange for a toilet in my hunting cabin. Being my first install, I wanted to get input on my success, or failure? I think I did it correctly:

1. 3" PVC
2. Cut off level with the cement floor
3. 3" Flange insert (has a rubber boot, and the flange goes inside the 3" pipe)
4. I screwed the flange into the concrete using two tap screws (I believe that's what they're called)
5. Under the flange, I used two rubber boots (donut shaped) to fill a 1/4" gap under the flange, between the flange and conrete.
6. The flange is fairly level, but could be improved

Questions:
1. Does the flange need to sit level, left to right, and back to front when a level is placed on top?
2. Are the rubber boots okay? Acting like a shim...
3. I used two screws to mount the flange, should I utilize the other 4 holes on the flange, and secure with an additional 4 screws into the conrete?

The flange needs to sit on the finished floor with no rubber under it. Personaly I would not use that flange. I would glue one on.

flange

1. I would never use a flange that inserts into 3" pipe.
2. But if I did, I would use one that glued in since the opening in the flange would have to be even smaller if it had to accomodate a rubber "boot" on the outside.
3. I would also never use a flange that did not have a metal ring for securing the toilet.
4. If the flange is not so high that it interferes with the toilet setting on the floor, then it makes little difference whether it is sitting on the finish floor or level.