Husband recently completed a MOST form and he surprised me saying he wanted CPR & ventilator which totally contradicts his adv. directive.

Thank you for your comforting words. Yes, I know what he would have wanted pre dementia and will not call EMS if things worsen with no chance of recovery. Will love him to the end.

Has he been declared incompetent? If so, you should have the MOST form invalidated and his advanced directive would stand.

I would abide by whatever. he filled out when he was of sound mind.

As POA you carry forth the wishes of the person you are acting for according to their wishes when they are mentally capable of making decisions for yourself. You make decisions FOR them according to your understanding of their wishes when they are no longer mentally capable of making their own choices. Only you, as your Husand's POA can KNOW as he is completing these forms, if he still has the mentation capable of understanding what it is to be on a ventilator, and what it means to have someone pounding on his chest to no avail.
Do know that with a YES to CPR, it will be done when he is found without pulse or breath, and no one will make a call BEFORE it is done to you. As to a ventilator you would probably be asked, but not before he is intubated by emergency personnel. I would redo theses form with husand and personnel when Covid-19 is over and you can be there to participate with him. Explain exactly what each thing means. There are different ways to say this. For instance, "WHEN YOU DIE, do you want us to attempt to bring you back again by pushing on your chest and heart?" and "When you can't breath do you want us to put tubes down your throat and push air into your lungs". Most people, even with dementia will tell you no, because it makes it sound EXACTLY as invasive as it really is.
Ultimately, they are correct. Your husband can say what he wants now. You can say what is to be done, as you understood his wishes, when he cannot make his wishes known.
Why they would make out the MOST Form with a demented person without your participation as his advocate is an entirely other subject for another day.
If your husband is remaining at home with you, and you are comfortable in knowing his wishes over a lifetime (I am about my own partner), then for you a MOST will not come into play until and unless the Emergency personnel are called. They will not intubate and do CPR on a person who is clearly incapable of coming back. That is to say, someone who is cold and has the onset of rigor. So for you, the avoiding of an assault on your husband's body will be ascertaining by the timeliness of your call to Emergency Services. You have the POA Advanced directives with you, that were done when he was capable of making his wishes known. This means you are not under any obligation to call EMT at all. You can instead inform his physician of his death. However, if your husband is in placement in care, then this does become a problem.