We rode it a couple years ago. We camped on Orcas and drove to San Juan and Lopez. So I'm sorry I can't answer most of your questions, but we had a great time. Talk about beautiful!

Check the WA state ferry site. You may be able to leave your car in Anacortes at the terminal (or possibly get some info about parking). The terminal is not in the heart of town, but a bit out of town.

Lopez has several hills but none too steep. Cute little town across the island from the ferry dock. I remember good ice cream! Quite country roads. Not a whole lot there as far as accommodations and restaurants. As we only spent the day, we had dinner in Anacortes. We had a great time and would go back again.
Also check with their Chamber of Commerce or tourism site. I know there is at least one motel.

Good luck finding info. You have a great time ahead of you. Can't wait for your ride report!