Me. Same age as yours. Lost everything, prayed for death every day for years. But things changed - I believe am much more happy and peaceful than ever. I started earning again (not as much as earlier but still enough for me and family). The turnaround for me was step by step and gradual, nothing dramatic. But what helped was seeking help. Pls find someone to listen to you - within family , friends , someone whom you can sit and talk to. This helps. I did not seek a professional therapist (where I live its not common), but I got lucky. Things moved gradually step by step, I lived a minimalist life , prioritised things which were important to me.

I wish you good luck.

You say: >> I know the best of my life is behind me, but I need help salvaging what's left of it.

You really don't know if this is correct - you don't know what's in future for you, without that you cannot say the best of life is behind. Drop that thought and seek help.