I'm so sorry for everything you went through. As others have mentioned, it's not "just" the loss of your partner, but also the routine you had, the reason to get up in the morning and do your thing, and taking care of yourself. So, first thing's first... Don't kick yourself around about the croissants. Nor the nutella. If it was what you needed right then, you know what... Whatever! I hope it scratched the itch and tasted great. The comfort eating is a result of everything you've been through, so you do get a free pass.
Now, grief.... It takes time. After about a year you'll feel a little more like functioning as before again, after 3 years or thereabouts, your life'll be whatever the new normal is, so.... Give yourself time. To grieve, to adjust. Maybe to indeed get a little help in terms of talking therapy, maybe join a group where people get together for this or that a day or so in the week, just so you can reconnect with people some. (Being a carer is often a lonely task, after all, and often, social life suffers). Not per se a grief group, maybe just something like, I don't know.... Red Hat Ladies? Do things that used to make you happy, if you can. If you find a little comfort in, I don't know, feeding ducks in a park or something, you're giving them the bread, not having it yourself. After a while you'll find you'll smile in spite of yourself. (I remember being startled by the sound of my own laughter a little over a year in, I hadn't heard it since my Doug passed, when I was 18). Anyway.... Talk. To anyone you feel comfortable with; a shrink, a friend, a stranger. If you can, and want to, of course. Maybe have a spot of tea at a nice place, just... Do kind things for yourself. It might not feel like it at first, but it'll help eventually.
CBD can help with sleep, but it can leave you a bit groggy in the daytime, and it might clash with the antidepressant, so careful with that. (Mom mixed CBD with her amytriptiline and her heart went nuts). As for the PF, you might want to talk to an occupational therapist. See how you can still do the things you want to do. Because you know what? It's OKAY to sit down during a walk. When my husband got Long Covid, he could walk 400 meters, and then had to rest for half an hour. Then 400 meters back home, and rest the remainder of the day. Everyone starts somewhere. Figure out what you can do, what you want to do, and how that can be achieved. Where are the benches, where are coffee shops, places where you can take a moment and regain your breath and energy before continuing on. Would a bicycle help, maybe one with a little battery assistance? Look at what could make your life work for you, again. Might not be easy, but you need to take care of you now, in whatever way, shape or form that may be. And hey, if you want comfort food... Pork scratchings, hard cheeses, bacon, olives, they won't raise blood sugars and are nicely decadent. Maybe throw in some Lindt 85% or higher for the chocolate kick.
You'll get through this. It'll take time, but you will.
Hugs,
Jo