I don't really know what I expect in the way of advice, but here goes. . .
This situation has been going on for a few years. I feel trapped and depressed about it.
Basically, my MIL is (I believe) mentally unstable and interferes constantly. My partner is spineless and at ties does stand up for me and 'our' family, at times lets her get on with it and says he "won't get involved", and at other times actually CLEARLY sides with MIL and goes against me and joins in with her bullying manipulative ways. To be honest, which one of these options he follows depends on what best suits him at the time. This issue, amongst other issues between us means our relationship which could barely be called that, is hanging by a thread / stalemate and has been for some time anyway, and i have lost most of my respect for him because of this issue.
MIL openly believes and says that I am a bad mother. When I am not, and there is NO evidence, neither does any health professional think or anyone I know think that I am a "bad mother". She will do this slyly, by making comments etc, but she will also say those words openly.
She is a drama queen. Drinks super strength lager every night and will then text or call hysterically.
My partner has been setting up a new business the past 3 years which only this past year has started to generate reliable income. Before this I worked full time to bridge the gap. MIL has commented that I "care about money more than I care about children"
I am "no good for her son" . She begged him to reconsider us moving in together many years ago.
Every argument me and my partner have she gets involved in it. I certainly don't tell her of these rows, he must do so. But she will start "defending" her son and raising her arms, screaming at me as soon as I walk into her house to collect DS (more on that later). Partner has been working very long hours to set up the business but it was having strain on the family so we agreed he would have one full day off a week. When she heard of this, she said that I was henpecking him and controlling him and what did I want him to do, become a house husband or something ? (erm no just spend time with his family!).
She is hysterical, oftens infers meanings that aren't there, she is over the top with the DCs (we have 2 one is 8 and the other 3) - all over them, over the top smothering affection all the time. I know, I know, you can't give a child too much affection, but I mean she is hugging and squeezing and shrieking and coo-ing even when they are running away trying to play. If some aqaintance makes a passing remark, like the other day an little old lady said about DS "oh you are too big to be in a buggy, you are a big boy", MIL went MAD and started telling the woman off 
.
She believes that because I am not like her, I'm more private in my affections and I'm not over the top when it comes to the DC, then I am - quote - "not bonding with DS" (he is 3!!! and bonded with him from birth ffs!) and that I "don't communicate properly" with my children!
I find her stressful when she is being "nice" and horrendously depressing when she is being difficult.
I would honestly be thankful never to have to speak to her again. However the issue is childcare. I still work part time although I have cut my hours down - I have to. Financially we need my wage it's as simple as that. I don't love my work, it's OK enjoy parts, hate other parts.
I work 9-2 Monday to Fri. DD at school and DS has to go to MIL 3 of these days despite me having to run around like a headless chicken going out of my way to drop him off and pick him up at her house 30 mins away, because my partner 'doesn't believe in childminders' says 'no way' to the DC having a childminder, even a very professional registered CM lady I've known for years who lives in same street!
MIL has DS 3-4 days a week whilst I work (just 9-2 hours though). She does not discipline him at all. Ignores anything me or P have asked her to do / not to do with DS (for example no hard lollipops, still feel he is too young - she just ignores and gives DS them anyway 
) . If DS is having a tantrum, she cannot cope - she starts crying herself!!! and gets hysterical at the slightest things, escalating DS behaviour. Threatens but does not follow through. I believe her mad behaviour is affecting DS and I really worry about this.
However P still will not agree to a childminder no matter what. So I am stuck really. It is so strained when I do pick ups.
I asked my partner last week to have words with her about something regarding DS behaviour and what she was doing in regards to it (going off crying when DS has a tantrum). Ie to tell her that it will confuse and upset DS seeing that. He went away to speak to her. About half an hour later she INFORMS me that I will need to make other childcare arrangements as she will not be doing it anymore, because I am "blaming" her for youngest's tantrums (!). Well hallelujah, I'd love to make other arrangements! This is the third time in 2 years she has threatened the "well I am not going to look after children for you then" , stupid childish ploy. She has in the past retracted her statement a few days later. She doesn't seem to get that I would dearly love to use childminder instead of dealing with her drama. But P won't have a childminders, nothing but his own angelic mother (to him). She cannot just decide when to take a little strop and
How do i cope with this until DS is at school at the least. I feel so trapped by it and depressed if I'm honest.