Well to start with, I don't agree with "the Knicks are most likely going to miss the playoffs" because it's a gross oversimplification. How far can Melo take them? His averages in our wins are right around his career averages, which suggests that Melo at his typical production gives us a solid shot at the playoffs. So theoretically, if he gets back to healthy Melo, we should be competitive and get closer to 40 wins than 35. Even so, I fully acknowledge that there's gonna be a real battle for 7th and 8th and that might not be enough to get them there...but that doesn't preclude me to dealing him in a rush since we don't have a draft pick anyway and my belief is we'll get better offers in the offseason. At that time there will be teams who miss on the max FA's available and will need to bounce back on alternatives. Melo would become an attractive option when he otherwise wouldn't have been.
So if the Knicks are out of the playoff race by the deadline, the Rockets still have to give me a BIG return. Otherwise, I'll hold off based on an educated risk. I'd be counting on his knee improving and thus his play improving which would in turn increase his value. I'd also count on the teams who miss on FA's being more open to a deal for Melo than they would have been (and in that scenario they can eat his contract without us having to match contracts). So this is not to advocate hanging on to Melo at all costs at all. This is saying that I believe the best way to maximize his value is a more patient approach and that would also buy us more time (and information) to have clarity in our next roster moves.
They are most likely going to miss the playoffs, you can call it what you want but the fact remains there are teams better situated for making a run than they are. The problem with your stats are that the Knicks are 4-10 vs teams above .500 and Melo's best games have come vs so-so teams. Lets stop and analyze this real quick, we're talking about a max player here and the goal is getting the 7th or 8th seed. The East is no longer that weak, and he's not as good as he was 3 years ago, if they can't make the playoffs with him there's no point in having him. He has a NTC, you're not going to be able to move him to whoever you want in the offseason and if he continues playing like he has then his value will drop.
The best way to maximize his value is to trade him while his value is still high, and he has a NTC so getting a big return on him isn't likely since he can pick his destination. He's 31, you're counting on him getting better or returning to form after a knee surgery? You're not getting big returns in the offseason, you're getting them from a team that is desperate, if the Heat fall out the playoff race you take aim at them, if the Rockets continue to stink it up you go to them. That is how you get the best value for him, not by waiting for him to turn 32 and have scouts take a closer look at him during the season.