I think in an ideal world married couples would share finances....but also in an ideal world everyone would be able bodied. And those of us unlucky enough to be disabled would not have to fight tooth and nail for everything from help to respect to empathy.
Working on the assumption that the PIP was assessed and paid out in 6 months (unlikely) and that OP got only the higher rate mobility then that makes her husband's income at min 40k.
This means no grants/charities will be available.
By OP's admission his wage covers the household expenses even without her working, so in theory her PIP could be used for exactly what it was intended...giving her personal independence. And it is the OP that gets to chose what is best for that. Not her husband, not even an OT as they often don't assess for electric wheelchairs in case they are then forced to fund them.
Why, if it can be afforded, would you want to make your partner's life more restricted? Why would you not want to help? The fact that his thought is not first how this money can help his wife and that carpet is more important tells you his priorities.
Also....please tell me how the OP is supposed to leave him? Try finding an adapted bungalow as a private tenant when your own income is "benefits". They sat letting agents are no longer allowed to say "no DSS" but they still discriminate. Try finding a council one...well you are waiting for existing tenants to die.
Also, sometimes simply existing takes up the only spoons you have, let alone all the hoop jumping for forms etc.
You cannot trust your husband to have your best interests at heart so you ring fence your PIP.
Life with a disability is not like waiting for a broken arm or leg to mend. It immediately makes people regard you as less than, including yourself if you are not careful, scrounger or a malingerer. Newsflash...no one wants to be disabled!