Welcome to TP, Sheena.
I hope you feel the strength that comes from others supporting you and understanding how you are feeling. This illness is often described as 'the long goodbye' and that really does sum it up very well. It is heartbreaking to see your loved one change in such a way, particularly hard, I would imagine, when it's your partner. As you say the illness not only robs you of the person, but your hopes for the future too, your retirement plans and so on. Depending on how the illness progresses, and the individual, your husband may or may not come to accept that he has dementia. In my father's case he never understood that there was anything wrong with him- he always blamed the external world for being 'wrong'. The only positive about this was that he never had to face the reality of how the illness would eventually destroy him. However he did move into a new phase where he was more accepting of his limitations - he stopped insisting he could drive, for example. Unfortunately the full time carer sometimes must seem like an over strict parent or even a prison guard, to the person with dementia, always stopping them from doing things they know they are perfectly capable of doing! Generally speaking, it is better to 'go with the flow' as much as possible, deflecting and defusing rather than diasgreeing with them , though sometimes of course, you have to insist on something. I drew the line at dad going out in his pyjamas, for example!
No-one can take away or lessen the hurt you must feel, Sheena, when your husband is being so difficult with you. As others have said, try to remember it is the illness, not the person. Imagine a gremlin is inhabiting your husband and making him say those things, which are so contrary to his real nature. Following up my reference to the illness being 'the long goodbye' I feel it is helpful, if you can, to keep up as many contacts and activities as possible with friends and family. Also try to share the burden with others, so that you get some time to yourself to refresh your energy. I suspect your husband won't accept 'carers' at this stage, so I appreciate how difficult this might be. However as the illness progresses you need to be able to have some life of your own, some small pleasures to enjoy, if you are to remain strong enough to continue coping with pressures, so take any opportunities you can to do some things without him.
This illness is cruel but you will cope. Cry when you need to, get as much help and support as you can from others, including TP. Cope with things a day at a time.
Thinking of you,
Blue sea