A warm welcome to the forum.
I’m sorry to hear about the deteriorating health of your Mother’s partner. We have Parkinson’s nurses on our helpline at 0808 800 0303 who can help you with any queries that you have regarding any Parkinson’s related symptoms.
However, I would definitely recommend you contact his GP if his condition continues to worsen or contact emergency services (999/112).
Do keep us posted on how you get on and please let us know if you have any other questions.