Regarding Neymar Jr's possible return to Barcelona, it's hard to predict. Like you mentioned, he left Barcelona mainly not to be under Lionel Messi's shadow. However, with Messi now at Paris Saint Germain, the dynamics would be different should he return. Also, a player's comfort and happiness are important and should be considered as well. He has indeed been plagued by injuries recently so that's another factor to take into account.
Chelsea situation involving Ben Chilwell, it's true that he's a valuable player. His versatility is indeed an asset, but consistent injuries can be a major hindrance. Under the guidance of Enzo Maresca, it would be interesting to see how he fits in once he fully recovers.
By the way Messi is now in MLS.
Personally I doubt that Neymar will return to Barcelona to help them after his contract ends with Al Hilal, because does Barcelona really want him back? I have not received any definite news about it, especially with the injury that is still a problem for him, it will definitely be a consideration for Barcelona, because the risk will be very big.
Just imagine, now Barcelona still has problems with their finances, and when Neymar returns to them with the risk of injury then it will be another burden for them. Now Al Hilal with their stable finances complains because their players do not give them anything.