Seems like you keep mentioning that PAT is hard for you, so I'd practice some harder PAT stuff like achiever if you can. Achiever RC can also help, since 20 on topscore RC is a bit low for pure search and destroy.
Practice score do not mean anything. But yeah you are in good shape. But dont let that get to you keep reviewing and keep taking practice tests. usually the pattern is that you will do couple points higher or lower than topscore.
usually, you get higher or lower on the real DAT. i actually got around the same scores on my topscore and was worried but dont get too discouraged! i did a lot better on my real DAT when i was only getting AA scores around a 20. Just keep practicing!