As for memorizing tunes, try to recognize patterns such as "stock" chord progressions like (I vi ii V) . You should have a good understand the relationship between the melody and how it relates to the chord. Basic music theory can get you pretty far!

Also this might be too obvious, but rehearse for your gigs! You may have over 3000 songs in your book, but your not going play them all at one gig. Try to figure what your client wants and focus your practice on the tunes that fit for the event.