Space 220 Lounge and SciFi are going to be the hardest to get and the hardest to pick up later.
For most other things, if you miss out on getting them on ADR days, you'll be able to find them as your trip gets closer.
Also, if you don't get the Spice Road Table party, fireworks at Epcot are very easy to see from all around the world showcase. Spice Road Table is one of our favorites though, and you can get on the walk up list for food throughout the day. Hummus fries are the BEST.
Even on New Year's Eve Oga's reservations were popping up all over the place. We've done two NYE trips since it's been open and it has not been hard to get for parties of two or four (not sure how many you'll be with)
My best advice is to not stress over dining. It will not make or break your trip. If you sign up for dining alerts with Touring Plans (there are other services, but they have not worked that well for me) or just check off and on as your trip gets closer you'll likely find what you're looking for. Don't panic if you get up early on ADR day and things aren't showing as available. Some places do not release their inventory immediately. Fireworks packages are notorious for this, and threads will show up here on the Dis with others in the same situation, and you can kind of keep an eye on that to see when they do start becoming available.
Good luck and most of all - have fun on your trip!!