If your D's do have genuine concerns about your partner Lucyloo that certainly doesn't excuse you being verbally abused and bullying is completely unacceptable.
You have the right to choose your partner, just as they have the right to choose theirs. I wonder how they'd have felt if you estranged them and/or verbally bullied them because you disapproved of their choice of partner.
To still be behaving this way 15 years after the death of your H, their father IMO, shows they have some growing up to do.
As for no longer wishing to argue, I'm not surprised as you've probably had enough of that now to last a life time. It would be an idea to discuss with your GP in case you are depressed but certainly have a chat to your partner about it and explain how you feel and why. .
What is a reasonable minimum spend for an online grocery delivery??