I'm a dummy and know nothing about anything, but it sounds like for your partners sake, maybe you are working too much. I think your feelings are valid and are handling the situation really well, but I think his feelings about your work/life balance are valid too.

If you have the option, maybe hit the brakes on work a bit. If you can't, or would lose your job, I suppose it is what it is and you guys just need to tough it out for a while. I get a lot of people don't have the luxury to just stop working as much. The 5 day work trip after what sounds like a few months of relationship tension caused by overworking probably sting. I think I would feel hurt by that.

I also think your partner threating to leave you is a little alarming. It sounds like they need a temperature check on how they feel about the relationship outside of the work issue. It could just be heightened emotions, or there could be something else underlying. Better to talk it out than let it fester.

The above is just my thoughts. Again, I'm just a stranger on the internet without clear context and perspective. I suppose my advice is to reflect on if you need to work as much as you do. If so, maybe your partner need sto reflect on the circumstances in which you are forced to work 60 hour weeks.

It's a tough spot to be in. Maybe you guys can set a soft target of when to expect a return to normalcy, whatever that may mean for you both.

Best of luck and sorry about your doggy. I hope things work out.