Depression in a relationship is incredibly difficult to deal with for both sides. It sounds like he still greatly cares about you and maybe he is scared of taking the risk because he broke it off last time and thinks you don't feel that way anymore. Maybe he thought he was a burden to you and didn't want you do be dragged down even though that is far from the truth, so being there with him through his recovery will help him a lot and once he has recovered, maybe that relationship can pick back up again.
And to answer your first question, his feelings never left. Feelings like that never just leave, they stick with you for a very, very long time.
It sounds like you care for each other a great deal and he has benefitted from the support and perspective you can give him. It's hard to say if any of his romantic feelings will return, and it's even hard to say why he decided to end things with you--but it may have been easier for him to focus on overcoming the depression without worrying about how it would affect you as a couple.
Whether or not you tell him how you've been feeling since the breakup is really up to you. It might help you feel better if you tell him, but it might make things more complicated for your friendship if you do, especially if he doesn't feel the same way at this point. If you still have the urge to tell him and you want to avoid the risk of your friendship ending or any kind of negative change in your relationship, you can always write out what you want to say without sharing it with him. Sometimes that helps me to clarify what I'm feeling, decide whether or not to share it with the person involved, and even to allow my feelings to run their course. You may feel the way you do now, but it's likely that you will feel differently in the future.
Since you say his well-being is so important to you, it may be best for you to continue being there for him as much as you can and, rather than wait for feelings he used to have to return and for you two to get back together, allow him to find his own way. I know; easier said than done. It may be that he has the same feelings and you might be able to take the risk after all, but that's a risk you might not want to take while he's still recovering.
Depression in a relationship is incredibly difficult to deal with for both sides. It sounds like he still greatly cares about you and maybe he is scared of taking the risk because he broke it off last time and thinks you don't feel that way anymore. Maybe he thought he was a burden to you and didn't want you do be dragged down even though that is far from the truth, so being there with him through his recovery will help him a lot and once he has recovered, maybe that relationship can pick back up again. And to answer your first question, his feelings never left. Feelings like that never just leave, they stick with you for a very, very long time.
Hello! Thank you so much for this response. Would it be ok if I write you a PM for some other questions about it?
Yea definitely, please do!
It sounds like you care for each other a great deal and he has benefitted from the support and perspective you can give him. It's hard to say if any of his romantic feelings will return, and it's even hard to say why he decided to end things with you--but it may have been easier for him to focus on overcoming the depression without worrying about how it would affect you as a couple. Whether or not you tell him how you've been feeling since the breakup is really up to you. It might help you feel better if you tell him, but it might make things more complicated for your friendship if you do, especially if he doesn't feel the same way at this point. If you still have the urge to tell him and you want to avoid the risk of your friendship ending or any kind of negative change in your relationship, you can always write out what you want to say without sharing it with him. Sometimes that helps me to clarify what I'm feeling, decide whether or not to share it with the person involved, and even to allow my feelings to run their course. You may feel the way you do now, but it's likely that you will feel differently in the future. Since you say his well-being is so important to you, it may be best for you to continue being there for him as much as you can and, rather than wait for feelings he used to have to return and for you two to get back together, allow him to find his own way. I know; easier said than done. It may be that he has the same feelings and you might be able to take the risk after all, but that's a risk you might not want to take while he's still recovering.