It really is up to you to look after DH at this time. Speak to your own GP (or better still make an appointment for yourself face to face), write down everything you have noticed and give the GP the list. Ask for their advice as to how to proceed. Let them know how worried you are and how it is difficult to cope with.
If it is the beginning of dementia - the sooner it is known about the better. It may, however, be something totally different and again, treatment can begin.
Definitely do not let him drive - lose the keys if necessary, puncture the tyres or whatever you need to do.
Is it me or am I getting mixed messages
How do you acknowledge Easter.