Supporting partners with mental illness :seeking advice

My husband has been diagnosed with:

PTSD

clinical depression

ADHD

Bipolar disorder

I knew when I met him he had some issues from an extremely terrible childhood abused raped and continuously sexually assaulted then homeless at 17. But I feel in love with him bc he was a strong person. He was and is resilient.

We’ve been together 5 years. We have one kid and another on the way. Ever since we got married 4 years ago he’s started to really change and I suggested he go talk to someone which resulted in these diagnoses

He’s just started taking meds for all this but I’m wondering:

How do I support him through this ?

How do I explain his mood swings to our toddler ?

What’s the point where I love him but ... walk away ? FYI this isn’t something I want to do but recently his mood swings where he just snaps have been really upsetting both me and now our two year old.

How long will it take for meds to work ?

I feel like I’m on eggshells with him these days. He’s so fragile and idk what’s going to make him upset with me or send him into a depression

Also we’re both going to couples therapy

What else can or should I be doing ?