I sync my axe to ableton via usb (custom 5meter cable with powered belkin hub (took a yr to find a working set) and connect the RJM thru powered Midi to the axe. The hub handles the vocals, dmxis, axe and mixer. The axe has both usb and midi cables in, and another midi out to my g-force unit. I COULD use the usb on the rjm, but i really dont want more than one cable. As far as overloading the midi chain, a tempo sent every quarter note is like a drip from a faucet, not to worry. Have you tried to activate 'link' in ableton and lock to the keyboard's cpu with yours? I dont know, but if you are running a cpu along with his, you should be able to sync the two, tho i dont trust wifi much for live shows. If you can get a midi out cable, you can probably sync via midi into the RJM and then sync the axe to the RJM. I would think it makes more sense to sync the axe and just let the RJM be an island.
I havent found much point in syncing the RJM to the daw.. Reality is, the RJM doesnt really have anything to do with timing, other than watching my tempo light blink. I have synced it in the past via usb, while sending midi out to the axe. In the end, I didnt like so many cables at my feet, so.. Even the tempo light has little use because of the latency, tho i like it being there to aid in how fast I start a song. I use the RJM for a tap tempo command in ableton, but thats not really sync anyhow.
You can dig thru settings and get the axe OR the mmgt to respond to midi individually. The rjm doenst need to accept messages IF you are letting the axe see them instead. I am going to be programming axe changes live thru the daw via clips, but this opens an entirely new can of worms.
I have decided it easiest to NOT try and rely on the rjm for timing. Even when it is synced, the latency in the lights make it hard to lock to in person. The axe syncs pretty good tho. I feel im not of much help, theres just too many variables to consider, and its all so damn finicky.
Best to review and write down EXACTLY what you are trying to accomplish and why. I have spent hours running circles and in the end, I got what i wanted, just not as easily as I had hope, and not how I thought it would go. In the end it wound up being.
Daw usb out (daw master clock), into the axe fx (slaved). Bi-directional powered midi cable from the axe TO the Rjm. Clock on the RJM is OFF, tempo is NOT SHOWN. I made a button labeled 'tempo', set it to blink with tempo, and made it for 'on messages' only. This setup keeps the axe (the sound generator anyhow) synced with NO issues. I can still control tap tempo in ableton via a button on the RJM, but its pretty damn tough to tap just right anyhow, so i dont bother.
I run a one man show, so my needs are kind of excessive. If you dont need automation because you have a band doing things, try to keep it as simple as possible. Allowing someone else to control the tempo and just locking to them, would be much easier than trying to manage it all yourself at the same time. It all adds up fast. Toss in a lighting track, a click track, some automated patch changes and a few other hardware devices on the chain.... whew, makes my head hurt. Fwiw, 5meters is about as long as you can get on usb. IF you need usb extensions, I have found the 'amazon' brand female to male are surprisingly good cables. Nothing beats a solid cable however. Always buy 2 if youre going to. My setup only allows me to be 15' from the mixer to the computer hiding on stage.
Oh, ableton sends a re-sync message everytime you hit 'play' btw. You can overcome drift easily by stopping between songs and then going to a marker in ableton or a clip and just simply hitting launch or play.