Maybe the other games weren't as easy targets to infilitrate as Sugar Rush.
Or it could be Turbo was only interested in racing games.
Basically, he'd have to manually reprogram to code for each game to take over all of them.
And keep in mind there is only one Turbo, he can't be in every game at once.
And yes, the laws of high energy physics would be that whatever energy generation device was powering his gauntlet would have quite a significant charge.
Even more so, considering that zero point energy requires the highest level of energy generation there is.
And another point to consider, Syndrome actually has a minibomb in his gauntlet!
We see him use it to try to kill Mr Incredible and the explosion is fairly large for such a small device.
So, obviously, he's not really bothered by having explosive devices on his arm.
And the zero point field is not a barrier, it's just an immobilization field.
In the movie, we see Mr Incredible take damage through the field, if it was truly a shield, he wouldn't be harmed by Syndrome slamming him against things.
Another point, we see that Violet's shield cuts through the zero point beams restraining her, so that's more evidence it's not a shield at all, otherwise she wouldn't be able to do that.
Also, consider that the final Omnidroid uses a zero point energy gun, but has no shield whatsoever.
If Syndrome had really created a zero point energy shield, he'd have installed it on the Omnidroid as added protection.
Regarding the jetboot, Syndrome struggles to stay flying using just one, so one alone isn't enough to get very far.
And it definitely wouldn't clear the blast radius in time.
As for the Underminer, it depends on whether or not the comics are considered canon.
That's a grey area, since Mesmerella (a villian from the Incredibles comic) has been canonized a little (she appeared in a disney parade float), but nothing else has.
I guess that's all we're going to get really, since if Incredibles was getting a sequel, they'd have had one by now.