well of course that advice is subjective and I really haven't seen your system first hand just basing my advice on your post..there should not be that much expansion directly on the tank, but if there is, than a bypass can help regulate that pressure by allowing some water to bypass them altogether. If a valve is installed in the bypass once it is adjusted to the amount of pressure you have coming in without damaging expansion it should no longer have such expansion and contraction extremes anymore and should extend the tanks life..
as for the temp of course it is also subjective, of course I was speaking in general terms but certainly it shouldn't be so hot as to burn bums....