It might be an issue depending on the amount of flow required by the feature.Just 1 more information : I hope that downgrading the impeler doesn't matter with this kind of pool (endless feature) which need water to overflow in a tank behind the pool.
Do you have a picture of the pool?
How much flow does the feature require?
You can go to a variable speed pump if you want or maybe try the smaller impeller to see if the feature still works.
If the pressure problem started only recently, then I would suspect a configuration problem or a defective piece of equipment.And 1 last question : I understand everything about the "sizing" of all the equipments and I will do it following your recommendations. BUT, the high pressure problem began about 2 months ago. In your opinion could it have been caused by an unfavorable evolution of the badly dimensioned system or will it be necessary to look for another cause even after having changed impeler and diffuser?
Since your system is more complicated than a regular residential system, you will probably need an onsite visit so that a qualified technician can carefully go over everything to see what the actual problem is.
Maybe a valve is set incorrectly or maybe a failed check valve or maybe something else.