Ladysui, I re read a post of yours in which you said when your son was 11/12 you left an abusive relationship with his father to avoid harm to you. Your decision but it does not mean your son is in any way obliged to return any favours, you did it to protect yourself, I didn’t read your son was ill treated by his father. I know you can’t drive now but you need to sort out which form of transport you will use to avoid asking him to give lifts.He is already guarantor to his mil, she should not have asked him, then you ask him, it must seem he is trapped. Any money you gave him and 100k is a lot, I feel it’s best they make their own way and live within their means, but that’s just me, it was a gift not to be repayed. I wonder if you’ve forgotten how your life is turned upside down by a new baby, made worse by the new mother’s mental health problems, you wanted your families help but they don’t. He must have been through a lot prior to you leaving his father, he would have known what was going on and the atmosphere at a very vulnerable age when boys in particular need their father.
I only say this so that you look at things from his point of view, to avoid estrangement because you will miss him. If you won’t compromise, you should tell him that, however I think if you did the relationship would be over. I would not be told what I could or should do, however I was never put in that position, once you got married my parents never gave unasked for advice or asked for anything. I think we all depend to a certain extent on our partners, I know how lost I felt for ages when my husband died but had been used to coping on my own when he was so ill. You coped when you left your husband 20 years ago and you will after losing your partner, it just takes time. Do what you think right for you, be handy to shops etc, vital if you don’t drive and dislike public transport.