Yea, I don't have any real troubles reading. (2 music degrees and 36 years teaching band, orchestra)
It's the jazz thing that hassles me. I get calls to do small ensemble gigs and I have learned how to get by, but I'd like to cure the problem rather than just use band-aids.
I'm really going down the rabbit hole here but I think that we are in the same boat- can play, can't improvise so well.
I was merely going to suggest some Aebersold stuff since you can read but having since read the entire IFR site and since you are already a well-advanced player, it seems that for the refundable cost of one private lesson it's worth a look, and presumably in an easier format than the Aebersold stuff. If it's as simple as skip-a-step like Malcolm suggests then you will continue to not be where you want to be- as I'm sure that you have already figured it out given your extensive experience in gigging jazz and from having been a teacher for so long. IFR does seem to endeavor to teach more than patterns which skip a step essentially is, though. On the other hand, Aebersold is totally jazz focused and doesn't teach patterns (well, not from the perspective of learning patterns as fretted instrument players refer to fingerboard box patterns). I'm guessing that you probably already know about Aebersold anyway.
I'm not a teacher and you are much more experienced than I am but since I have had many false starts with the same endeavor as yours: books; videos; scales; modes; teachers; and having since done much research I now know what I have to do and I'm guessing that you need to do it to so maybe I can motivate you or reaffirm what you already suspect.
Since teachers aren't banging down the door to opine here and since I suspect that you are like me in that you learned to read (follow the dots) but didn't learn to listen and hear how each note interacts, both harmonically and rhythmically (I have learned that you can do a tremendous amount of stuff with just a few notes and a boatload of rhythm, not just durational rhythm but through accenting various subdivisions of the beat as explained in the Fuqua link below), both with the other notes you are playing and with the overall harmony of the tune, I will throw in my 2 cents in the grand scheme of things. The problem with materials like this, including Aebersold or any method or even a teacher, is that they don't/can't possibly emphasize enough that YOU MUST LEARN TO HEAR BETTER. To be sure, Aebersold emphasizes it but it really is impossible to emphasize it enough so one must motivate one's self to get the most out of it. Never mind that a lot of teachers/players have such good ears that at this point in their lives they don't even remember what it's like to be us, or they never even were in our position as they were born with the ears.
You really have to hear. Have you read
REALLY Learning a tune (Fuqua)
In a nutshell, the above link demonstrates that one must really grind stuff in but not just mechanically/patterns-wise- one must actively grind stuff into the ear. Of course, I'm sure Ed Fuqua didn't wait to start gigging before he had done all of this extensive homework for every dang song that he ever played

so there must be some keys to start driving before you have an actual, proper license:
Weird scales. I think that someone with the mechanical skills and harmony understanding that you must already have could, indeed, go a long way further with your "couple of good ideas" idea. I think it would be learning some of the weird scales that jazzers use and then learning how/when they are applied. You can cheat by playing them by pattern for now while you grind stuff into your ear. It's those "weird" notes that all of the good improvisers can pull out of thin air that will separate them from us no matter how much other stuff we know. They are frequently using notes from crazy scales. I am learning that there are so many crazy ways to play all of the "wrong" notes. A lot of guys probably don't even know what they are doing as they just hear "out there" and a lot of guys probably don't like sharing their secrets for free (and I don't blame them). In fact, I play (in non-jazz settings) with a guy who can do it all- I'm talking Larry Carlton "out there-" and I like to pick his brain. If he thinks real hard about it he can explain a lot of what he does but the truth is that he doesn't think about it anymore when he is playing, he just hears it. And some stuff he can't even explain because he just "invented it" for himself and hasn't bothered to analyze why it works. For instance, he told me once "next time you go to play any pentatonic scale fill of some sort, play the first two notes a half-step lower than what the scale calls for then play the notes of the scale." That alone makes a huge difference and I'm sure it could be analyzed into being some scale; in fact, without having analyzed it, I note that if this were played from the minor pentatonic box it is very similar to the Super Locrian or altered or altered dominant or jazz melodic minor scale (I still haven't got all of these terms straight but I think all 4 of those are actually the same thing- and THAT nonsense alone is PART of the jazz "problem"). Here are a couple of links that someone of your ability should grasp and be able to apply rather quickly but don't forget the Fuqua work on hearing and don't forget that working on accenting different beat subdivisions can go a long way toward making just a few notes sound way more interesting.
This one is insane- one pattern in one position covers 4 keys. The same pattern in 2 different positions covers the other 8.
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Jazz scale - Wikipedia (pay special attention to the altered dominant scale)
I'm still learning how to more interestingly apply this stuff but I've had major break-thrus in the past few weeks that escaped me for years before. In just a couple hours you can learn to apply some crazy stuff. One is unlikely to just noodle upon these far out scales- the guys who do that are already just playing and not asking questions like we are. Damn them!

By the way the Aebersold stuff very methodically increases in difficulty within any Volume and, at least in the jazz improv books, does give extensive scale-type recommendations for given chords- I note that in his books and in other places, particular attention is paid to the V7 as if its the one that best allows you to go way off the reservation- this is just my casual observation and by no means gospel. It just keeps popping up.
Best of luck. Feel free to give me ideas or feedback!