Hmm, doesnt sound good. Poor flow rate after descaling - its very likely hard scale has been dislodged somewhere and found its way into the group head, probably at the mushroom, but it could be anywhere and youll have to find it via a process of elimination.
Another reason to BE PATIENT and only use the correct products- the Jura descaler you used is not designed for this purpose.
I suggest you read Chris excellent How to descale a HX machine properly sticky if you havent already.
The pressure gauge sitting higher than zero is perfectly fine, as the pump will continue to pressurise the heat exchanger loop even when the group valve has closed.