That is pretty much the same, as mine. Just mine does not have a built in WiFi on the electronics. Too bad, because mine is pretty much new
Can you tell me what is Mount Code of yours? It is on the 'Detailed Mount Information' tab in the INDI control panel. Mine is 152.

I think what you are doing is correct. I bet you mean by Synscan->Sync (right menu) Skywatcher AltAz -> Sync. Since there is no synscan involved in this process (that was your goal, right?)
As far as I understand the Alignment subsystem, you can repeat the Sync operation with more stars, and this will improve the tracking accuracy. This is not the same as with the Synscan handcontroller, no "two star alignment" or "3 star alignment", this is "many star alignment".
I don't know the limit, but definitelly can be done more than twice.

Also it is a big advantage of using INDI that you don't need to do it "by hand", plate solving is a great thing!. Just put your camera on the scope from the beginning, and use the alignment tab from EKOS! You don't need to find any known star. Just point your scope pretty much anywhere with a Goto operation (I normally start with polaris). It will not point to polaris of course, but now do a 'Solve and Sync' operation and you have a starting sync. Now goto to an other star, and repeat. The great thing is that you never have to 'center a star' by hand. Plate solving works even when there is no bright star in the field of view.

About tracking accuracy: 4 sec exposures is just what I got, most of the time. You will not like what I say, but these drivers are not production ready, IMHO. I try to make it better, but I just understand too little of how it works yet. I get better results with the Synscan handcontroller, and the synscan INDI driver. That works quite smoothly.
Also the tracking accuracy is greatly depends on what part of the sky is the target. It is the worth just on the zenit, since the mount has to turn azimuth quite quickly. There is an effect with AltAz mount that the field of view is rotating during tracking, and it is an uneliminatable effect without eqatorial setup. It is the worst on the zenit, and much better on the lower southern part of the sky (the stars are just moving right, azimuth only). Sometimes I can go up until 16 secs, but pretty much that is the upper limit. No multi minutes exposures possible with an AltAz mount.
A few night ago I tried to image M57 and M27. I got much much better results with M27, I bet because it was at lower altitude. M57 was just above my head. I did it one after the other, with the same alignment.

Also keep in mind, that the backlash of the mount should always be considered. Always end your centering operation with 'Up' and 'Right' motion. Otherwise the mount will not start following immediately, just after the backlash amount has been rotated. Just the same with the Synscan handcontroller. This is the property of the mechanic, cannot be eliminated.

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