I guess first up, what type of coffee are you using? Is it freshly roasted sourced locally or home roasted, for example?
Have you or someone else, adjusted the Silvias Over Pressure Valve to provide a 9 Bar pressure at the puck? Some of what you describe indicates that perhaps this has not been done. Silvias OPV can be factory set to 12 Bar or higher and this will severely effect the quality of shot that you are able to produce.
Your PID setpoint of 228deg F sounds pretty close and I would leave it at that for the time being.... no use introducing more variables into the mix. Everything else you describe about your technique sounds reasonable. There are other techniques you can try re: dosing and tamping, etc but the method youre using now is in the ballpark.
Freshly roasted coffee is essential to achieving quality shots and if the Brew Pressure is too high, you can end up with the results youre describing so I would address these two items first before going on with anything else. All the best,