A couple of things...
1. I don't like training for tests - meaning I don't like training for the 40 yard test, VJ, 225 test or whatever kind of "combine tests" are out there. The reason is that I don't think training for those tests results in better sport performance. I'd rather the tests reflect solid training and the results are "whatever". Meaning, the most important thing is whether or not you are performing better at your game, not on some random test.
2. Very few times in basketball does a VJ ever come into play. Even when rebounding, there is usually (not always) a step involved. I've worked with basketball players and have found MANY have very low vertical jumps. The reason is simple - they don't need them. If you are 7 feet tall with long arms, you don't need to a high VJ. Even more so, these guys can fly through the air AFTER running - a very different kind of jump. Granted jumping is important (obviously) but I don't think you need a test to confirm your jumping ability. Just like a basketball player (or really any sport) doesn't need to 1RM their squat or bench press.
3. When you are older or not "basketball gifted" - jumping is going to be a product of a couple of things: a) genetics (the most important) b) power (speed and strength) and c) related to (B)...your current bodyweight.
This is why, when training for sports, being "strong" is not important (500lbs bench press, 800lbs squat); however getting stronger is important. And yes, there is a point where getting stronger might not help your sport. Are you at that point? I have no idea - but when your quest to get to X weight hinders your sport performance, then we have a problem.
I know you want to dunk again but I think the most important thing to ask yourself is this: are you playing basketball at a level that you are happy with? THAT is the only question that matters.
Understand that the vertical jump is often a measure of athleticism; I've talked to two different coaches, one a legendary strength coach and another a defensive coordinator that coached in the SEC and the older SWC. Both of them tracked every starter for decades and what physical tests best indicated which players would be starter. Both of these coaches were independent of each other. And both had the VJ as one of the tests that indicated sport performance.
However, it's the "chicken/egg" debate. Did they test well in the vertical jump because they were great athletes or did they improve their vertical jump and the result was more playing time? I think we all know it's the former.
P.S. - I have no idea how to increase vertical jump.