Can self - pleasuring make intercourse feel less good?

Not at all, if anything, masturbation helps. It helps the flows of blood and increases your chance of climax.

I don't think so. However intercourse is something that takes practice with a steady partner to get it so it's really satisfying. A one time dip in the well is not much better than jerking off in her penis trap and jerking off is probably better because you have practiced it and know how to do it well.