Hi @andrea_robbins, welcome to the forum. It sounds like an incredibly tough and stressful situation you're in. Trying to manage your own challenges while supporting your husband can not be easy in any way!
I guess the main things to consider with him would be to listen and allow him to feel validated but just letting him know you're there for him and that you cant imagine how hard it is for him but you that can and want to listen to him. When he is open to talking, you could say to him that you've noticed that things seem more difficult since stopping his medication, and what does he think about seeing someone about exploring some other options that may help? This non-confrontation approach may help to convince him. I know you said he is resistant to counseling, but he may be encouraged by you working on your own your own self care and mental health by seeing the importance and benefits of speaking to a professional for help. It may also help him to reframe thoughts he may have of receive help for his mental health by reminding him that such help isn't about failure or weakness, but just a way to find a way through a very tough time, like a Captain needing a navigator.
Considering he has attempted suicide before, i think he really needs to organize a safety plan for himself. It's important to be direct with him if you feel he is unsafe and ask him, You can then help him step by step to create this plan so he has a list of what to do in a crisis situation or feels close to one. He'll also have a list of emergency contacts to call.
It seems that you are trying to do so much to support him, and yourself but it is important to remember that your own well being is important as well. It is okay to remind him of how much you care about him, but that you also need to occasionally take a moment or two for yourself, in order to support him as best you can. I can understand you saying you feel guilty and ashamed for not offering him what he needs, but in an extremely challenging situation like this, it is important to keep in mind that profession help is required to 'fix' your husband's depression, and that your job is to be there and support him. There are limits to what we can do and sometimes when things reach a crisis point it may be necessary to call in that professional support, even if he doesn't want it. At that point his safety is the priority.
I guess finally, even just asking him what he thinks may help. If if he cant answer, or just part answer, it may empower him to think more about his own well being. If you don't want to seem pushy, then focusing on caring for him, by asking him things like what he feels has been helping, or is there anything that may make things easier, or even just how he has been feeling recently.
"I" statements can also help to show your concern without making it sound like you're advising him of what to do. Things like "I have been worried about h"ow hard things have been for you and that you want to support you how every I can. Or just telling him "I love you and I just want to see you feeling like you're in a happier place." I think, basically, just frame things as 'offers', not advice, and if you dont get anywhere with him, you can always revisit it later rather than pushing it in the moment. Just by saying to him that you know that you've both discussed <whatever> before but that you just wanted to see if he's feeling any differently about it now. If he still doesn't want to talk, then just remember that sometimes, as a support, the best thing you can do is just be there with the person and sit quietly with them. It may even give him the space he needs to open up when he feels ready.
I wish you the best of luck, for your husband and yourself. Just remember to look after yourself as well and that its such an incredible amount you're dealing with between you both so don't feel like you're letting him down in any way. It seems to me like no one could ask for a person to do more for them! You've even signed up to that MH first aid course! You're are doing an amazing amount! Hopefully you husband sees and appreciates it and will start to be more open to some outside support, even if just to take some of that load off of you.