I would keep checking daily. I had multiple FP+ for both New Years week. They showed less than 2 weeks out. IMO, the MSEP FP+ is well worth it. You are in the hub right in front of and facing the castle. Plus, its not crowded in that location. The Wishes FP+ is OK. I can see it having more of a benefit when crowds are big and you dont want to be smashed with people. IMO, it is worth doing once since Tink flies right over you in the rose garden location (they may or may not let you on the grass). As far as fireworks viewing location, straight on to the castle is a better view. You can stay in the MSEP FP+ location but it is close to castle so some fireworks can be blocked even more so it if is windy since they might be set off lower in the air.
In the future, we would do MSEP FP+ again if is still offered. Wishes would be a maybe mostly depending on the expected crowd level. Its not a great view but it is a good view and not crowded.