Dear @Spana29
Welcome to the forums, so sorry that it is under such difficult circumstances. I'm so glad you have reached out.
It is very frightening and distressing when someone you care about is in this space. I would encourage you to be very firm and insistent on him seeing the GP for a referral. When my former partner has been in this sort of space (we both have PTSD) I have had to say to him "you need to get help because when you are in this space I don't feel safe". You don't mention whether you have children but if you do then it is worth pointing out how devastated they, or other close family/friends (whatever is appropriate for your circumstances) would be if he attempted to harm himself.
Make no mistake talking about suicide is a cry for help, even if he refuses to acknowledge it at the moment. You are right to take this seiously and be very determined that he gets help. I wouldn't threaten him, I'd just tell him straight that he needs to go. Rick is right, it will almost certainly get worse without intervention.
In the midst of this huge load you need to do all you can to get the help and support you need. Otherwise your own health will suffer too. Do you have a close friend or family member who you can talk to, and who can give you some comfort and moral support? Please don't think "I don't want to worry them" because what you need to consider is how they would feel if he were to harm himself and they had not known their help was needed. This is part of genuine friendships, they may be limited in what they can do, but someone who cares will be as supportive as possible - even if it's catching up for a regular cuppa and having some down time.
Feel free to come and "download" here as often as you wish, you are very welcome.
As Rick said - hope does endure...
Kindest regards,
Kristin