What a lot of listening to scanners you seem to do!!
My tuppenceworth:
Proceed direct to: A clearance to go direct to a point, maybe missing some intermediate ones out on the way.
Resume own navigation to: As already discussed, releasing someone off a radar heading. The point named may or may not mean missing out some intermediate ones.
Cleared to: General clearance, which can replace both of the above (in lose phraseology!) but could also take the form of a routing clearance given before departure. (E.g, Cleared to XXX via Airways YYY and ZZZ, climb FL AA, when instructed by radar FL BB, Squawk 1234".)
I'm sure others will have something to say as well.
------------------
"Take-off is optional, Landing is mandatory"