Hmm, I suppose at 5.6Kg + 2" diagonal + eyepieces, you may be getting close to (and above) the rated load capacity. But I would still think you'd be okay, for visual alone. Given I am in the same ballpark for weight (23-24lbs including CW), and I am imaging (visual weight limit is higher than for imaging). But perhaps one of the experts can weigh in? (gah... no pun intended! Haha)
In the mean time, I would refer you to the following thread re: weight limits for the various tripod configurations (perhaps you have seen this?):
Jerry has provided a very nice comparison chart between the different configurations (focused on upgrade price though, so not exactly what you're looking for). In addition to this, I think if you search around these forums, you will run across a few other folks pushing the weight limits of this mount quite successfully.
I believe Jerry has also mentioned in several posts that the internals (gear and motor system) in the iExos-100 is very similar to that of the EXOS2. And thus weight limits for the iExos-100 mount should actually not be too far off, if not for the smaller tripod. Again, perhaps one of the experts can confirm?
I am afraid I am unsure if adding the az adjuster alone will help increase payload capacity of the ST1 tripod. All I can relay is my experience. And as I say, I am already above the rated limits of the mount using the ST1 tripod for imaging. Nevertheless I am having great success with it. Perhaps this is, in part, due to the addition of the az adjuster.
Mounts: iExos-100 + ST1 Tripod + Az Adj
Scopes: WO Zenithstar 71 + 0.8x Flattener/Reducer, Celestron 5SE, Starfield 60mm guidescope
Cameras: Canon 60D (non-astro) main cam, ZWO ASI120MM Mini guide
Software/Computer: ASIair Pro