I have had a similar experience with my now-exP after I had a very traumatic experience (not a bereavement but very upsetting and led to me suffering anxiety and depression). ExP was supportive, or tried to b/appeared to be. But he became more difficult, hard to communicate with, passive-aggressive and did some things that really upset me "by mistake" or because he "forgot".
Like you I was the competent, do-it-all person in the relationship. He was usually the one who needed support and attention, in fact could be quite attention-seeking. At some level he clearly found it very hard that I was being needy or getting all the attention, even.
For this and a number of other reasons I ended the relationship a couple of years down the line, I'm not saying you should do the same, but yes I do think he should be able to support you and you should be able to be vulnerable - not leaning on him 24/7 for the whole relationship (which you're not), but to a reasonable degree in a give-and-take way, it's normal.
Maybe this situation his revealed an imbalance in the relationship, where you're the grown-up and he's really not. At the very least he needs to understand that you are allowed to have vulnerable times and you need to be able to talk this all through with him. If he won't, that is a problem I think.
Sorry for your loss and the tough time you're having –I hope it's not a platitude to say I predict you will eventually heal and recover, as I have.