When I changed dishes and the holes didn't match, I scraped off all of the old sealant, and, as you mentioned, filled all of the holes with self leveling Dicor.
RE, cable entries, there are a few available. I use (search on winegard cable entry plate). I have two of them on my Sunstar. I think both are the 4 cable models. Use Tacky Tape or butyl tape under the plate, and then seal the screw heads with self-leveling Dicor.
2014 Itasca Sunstar 31KE
1988 Itasca Suncruiser 31RQ
1968 Travco 21'