Where to start? I read your msg at a ridiculously early time this morning (insomnia) & it's been bothering me ever since. I wanted to say something but didn't want to come across as an arse...
You're being unnecessarily hard on yourself. You've had an awful lot to deal with in a short space of time. You can see how recent events have affected your other half, have given her leeway & understand her reactions but you don't do the same for yourself? It's fine being stoic but at the moment it's not helpful. You need to talk to her about your stuff. It may shift a lot of weight off your shoulders.
Covid has pushed a lot of us into a tailspin, even those who didn't have underlying problems. I've had depression 1/2 my life. My counsellor (by phone) has been a Godsend. I just need to vent mostly, I don't need someone to fix anything, I just need someone to listen. Also, I have used the Samaritans before - they're wonderful at listening, non-judgementally and confidentially and are patient.
You said you lost your best friend to suicide. I am so sorry. This in itself is a lot to deal with. Talking therapy might help you? Search online for help from suicide/bereavement charities?
And on that note, please don't. It sometimes just takes a little thing to dissuade you. The only time I thought seriously of chucking myself off a bridge (in Dublin) I realised I was wearing a brand new AV bench coat & didn't want to get it wrecked in the mud...
I hope some/any of this has helped. Feel free to give me a shout through DM. Take care.