1. Is there any reason you couldn't take him to daycare on your way to work?
2. Is there a reason your husband is siding with his mother over you?
My MIL is an awesome woman - she doesn't help in the grandma capacity, but she sure doesn't talk about me - to my face or behind my back. My husband wouldn't put up with it if she did. For that matter, neither would I.
Does your husband want a divorce? Is this some kind of passive - aggressive stance from him to get you to say, "It stops or I'm out of here"? If it is, then the two of you need counseling - not daycare advice. If it's not, then he needs to realize that that is where he is pushing you (if it is in fact where it is headed), and the two of you - again - need counseling in addition to daycare advice.
Is there a reason you can't stay at home? I am not being sarcastic - I swear.. between the cost of daycare, work clothes, and a second car, you may find you're working for a buck or two an hour.. and lots of times you can make that with part time work around your husband's schedule (presto, no daycare).
Barring that, I'd suggest a serious sit down talk with your MIL. Among talking points that you come up with, I suggest:
1. I know you love my husband and our son, and I don't want to discourage that relationship - but just as you would not put up with someone speaking untruthfully about you, I will not tolerate you talking poorly about me - especially to my son.
2. Lady, I am in this for the long term. Attempting to break up my marriage is likely to result ONLY in stress for your son, and should it work - it will result in your son (and you) only getting to see junior on the 1st, 3rd, and 5th weekend of the month + wednesdays. I don't want that. Not for my son, not for my marriage. I assume you feel the same way.
Those two points agreed upon, we need to come up with some ground rules so that you and I can create a doable relationship for both of us, so that we do not cause unwanted strain on the two of the most important guys in our lives.
Feel me? :)
S.