sugarpufffairy You are having a rotten time and it must be deeply distressing but if your DD and partner are both treating you badly, why on earth are you doing going round and doing decorating for them, still more ununderstandable why did you stay when your DD's partner started criticising the quality of your work? You should have downed tools and walked out.
However unhappy you are about your daughter and her partner, and given what you say, this is understandable, the cold unpalatable fact is that your daughter is an independent adult, as you are, and making her own choices and decisions about how she wants to live, however awful those decisions may be and however unhappy they make you.
I think you need to distance yourself physically and mentally from this household, physically by not going round and looking after the home, whether decorating or cooking and cleaning. Mentally, by telling them that you need several days notice before babysitting and when the babysitting request coincides with an arrangement you have made, tell them you cannot baby sit then because you will be elsewhere and then ignore the pleadings and attempts at emotional blackmail to get you to give way.
Currently by getting so emotional tangled up with them and giving so much practical help you are actually supporting the household and enabling it to keep functioning.
Stand back, leave your daughter to sort out her own problems. Once she knows you are not going to come running whenever she wants you, you may end up with the result you want.