Hello Linda
I'm sorry that your partner's condition has deteriorated so badly; it must be very difficult for you coping with all his needs.
I suppose the decision as to whether or not to apply for a change in award depends on whether your financial situation demands it; there is always a danger that you will lose the award you already have, however unfair this may be.
My personal inclination (and it is only personal) would be to leave things as they are until there is a necessary change to PIP; other members of the forum might have much better insight into what would happen if you decided to go ahead and ask for change of circumstances. You will be only too aware of the peculiarities (?!) of PIP.
Read what other people have to say and then decide. No one can make the decision for you, unfortunately.
Good wishes.