Hey @bun
I just wanted to say what a lovely and caring partner you are. It sounds like you're very supportive of him and it's very understandable that you're worried for him since you can't see him for a couple months. That must be hard... 😔
As someone who has really benefited from a great partner when I was feeling quite down, I can say that regular contact has helped a lot. Of course not overly often, but regular enough. I appreciated the little check-ins and asking how I was feeling. Sometimes he'd ask me to rate how I was on a scale of 1-10, and even if I hadn't, he'd have kept track and noticed if I said a number that meant I was feeling a little better than I was last time he asked. I think that encouraged me a lot.
Jokes help! Or a funny story. Anything that can make him laugh might help him. I also think assurance is key- I would say I also had a lot of self-doubt in the past. Having a partner there to reassure you of your talents, your beauties, your skills, your great personality, the proof of actual achievements they have done in the past etc.
Of course you know your partner best, so you can pick and choose what you feel he'd like based on his love language and other little things, but I hope some things that my partner has done to help me, can be suggestions for you too.
Please remember to look after yourself as well! Don't feel guilty taking time for yourself and doing the other things you love, or spending time with others you love in your life. I also agree with @Philippa-RO that kids helpline or headspace would be a good option if you feel he needs to talk to a therapist or other professional faster.
I hope you and your partner are doing well today ❤️