My MIL’s style of raising children and my style are also complete opposites. We took the most drastic step. My husband quit to become a SAHD and we raise our children. If my MIL does something like what yours does, if it’s a small thing, I try to let it go, to honour her. For bigger things, I’ll explain to her why I want to do it that way, and my husband’s also on the same page as me, so that helps. For huge issues, I let my husband do the talking.
For your case, seriously consider infant care? You’ll need to tell your husband how much all this is affecting you, and both of you need to establish common goals in raising your child. Only when both of you can see eye to eye, then both of you can tell your MIL how to take care of the child, or to tell your MIL that you’ll he sending your LO to infant care instead.