Never let him go!
The only thing you've been deprived of is his body.
The rest of him would've stayed with you, because it/he would not want to be far from you!
I sometimes say, "To do it, go through it." I stick with that. The most important woman who ever entered my life died and I simply won't let go...there is no need/obligation to let go, at all.
If you could say, aloud, who he'd sooner be with and answer yourself by saying "...with me", then only the body has left the scene of the loss.
On his birthday, wish him a happy birthday.
At Christmas, make room for him in your arrangements.
On Summer walks, assume him to be by your side, and smile, and be happy at that.
In his world, right now, you're the one without a body, remember. Live a long and active life and, when the time finally comes, you'll both be in the same frequency and you'll be bodies together, again. Don't rush that...just wait for it.
In the mean time, build something in his honour and memory, anyway!