Sounds like you're using stale coffee and a cheap grinder. If so, you really need to invest in a better grinder and fresh, high quality beans. Using stale coffee and an inferior grinder will never give you good results. If you're on a budget, you can get a decent hand grinder for under a hundred bucks.

As for temperature, my backup Gaggia does tend to run hot. It will flash boil if left on for a while, so flushing a few ounces through the group before brewing is mandatory to get rid of the bitter taste.

However, I think the OP's problems in this case stem from problems with the coffee and grinder, not the temperature of the brew water. Brew pressure is not usually the culprit in these cases, or at least not the principle offender.