First off, welcome back to brewing!
Some quick answers to your questions:
I normally make a starter with liquid yeast, but you can certainly pitch it right in form the vial. It will still work fine, it will just be a bit longer before you see airlock activity.
There should not be an issue waiting 8 hours as long as you kept the wort covered from the elements.
I leave all my ales in primary for 7-10 days. Wheats stay in primary for 2-3 weeks then go straight to bottles.
You absolutely can re-use a yeast cake. Siphon off as much of batch #1 from the yeast cake as you can, then just pour batch #2 right on top of it. Just be prepared for a much more agressive fermentation - a blow off might be required.