I would 1st find out when the last train leaves for Paris... then its a 45 minute or longer ride back into Paris...and do you have to change trains/metro to get back to the area your hotel is in.... then you still have to walk back to your hotel.. So you are talking about getting back to Paris around Midnight or later...
You might want to think about Ubering back to your hotel in Paris... It would be much more comfortable than being squished onto a train at the end of a long day...and a direct route...and this way you could eat dinner.
I would have suggested staying overnight at DLP at a Value this way you can enjoy the fireworks and everything it has to offer... but with going to Versailles the next day.. not unless you plan to go later in day to tour would this work out. Or if you did decided to stay at DLP 1 night you could go from DLP directly to Versailles... then back into Paris to your main hotel... If you could get a good rate it might be worth it... this way you can have dinner, then spend the night and get some extra sleep, before moving on to Versailles.
DH and I have done this a few times when we are vacationing somewhere and want to check out another area... we find a basic hotel for one night and just bring what we need for the next day...we don't check out of our main hotel...
We had some friend that just did this in Vegas... they were staying at the Rio ( for a week) and before they left she and I were talking and she was like we are so close to DL. I would love to go .... So I suggested this plan of attack... so they found a hotel near DL for around 125.00 I think it was like Holiday inn or Hilton garden inn, that offered free breakfast and transportation to the park...they just wanted a clean place, and hot shower for one night... They left Vegas early in the morning they left around 4:30am she said they just took clothes for the next day and a few grooming products, She said it was like around a 5 hour drive... they check in early parked the car... and caught the bus to the park... They did end up adding a extra day to their ticket to check out the other park... they stay till around 2pm then drove back to Vegas....
Whatever you decide have a wonderful time...