No not a good base for day trips. It's too far on winding roads.
Not really, as it's about a 2½ hour drive one way. If you are having trouble finding lodging, or lodging in your price range inside the park itself, look nearby, but outside the park boundaries.
If you click on the blue link below, you will find an excellent TripAdvisor Traveler Article that will give you lots and lots of excellent information about lodging around Yosemite:
So yes, you can travel all the way from Angels Camp to Yosemite Valley now (in May.) Expect the drive to take a few hours. Note that Yosemite is incredibly busy this year with parking lots filling early.