There's absolutely no way the Rockets should keep Dwight, long-term..he's already declining, and considering that he has a very low skill-level, he's going to continue deteriorating at a fast pace(not to mention he's injury prone, nowadays)..
Harden's style of play is toxic, but he's a monster player, tbh..sometimes players need to fail a few times to realize that they need to change their mindset, and/or they need a new coach/system..the Rockets just have a cancerous environment, right now, with too many limited players playing big minutes(Beverley and Brewer, in particular, neither guy should be anything more than an 8th or 9th man), and players not giving enough effort(Ariza, Harden, Lawson, Howard on some nights, etc)..
Hard-ass coaches like Thibs are becoming antiquated in today's league, but some teams really require it IMO..the Rockets are one of those teams..