2. Your degassing tool sounds fine. The only two things you need are to be able to easily sanitize it and that it agitates the wine enough to release suspended CO2.
3. Having the sugar on the lid isn’t a bad idea if you’re worried about pets or something messing with the lid. It may also hold it tight enough to keep flies out. It’s okay to keep your wine stored this way for about 5-7 days at which time I would expect it to slow down and move into secondary fermentation. At that point you’ll want to rack off the fruit (if there is any in there) and into a container such as carboys where you can attach an airlock.
4. No, you can use PET plastic carboy as well. Just be careful not to scratch the plastic when you clean them out. The scratches can become great places for spoilage micro-organisms to hide out.
5. My hydrometer goes from up to which envelopes the winemaking brix / SG range quite nicely.