heyy there, this is a really good start. Nothing much seems too off to me with the anatomy, the neck looks solid, and the new hands are definitely an improvement. The only thing I can see is it feels a bit "tame". Like a bodybuilder in a demon cosplay, as opposed to an actual demon. I played around with it a bit, and came up with some edits, most of which are more subjective than anything:
1: The bottom of the chest is usually closer to a full headlength down. Your higher chest is definitely within the realm of believability though, and could be a style/aesthetic thing.
2: With some slight variation in contour, you can bring more hardness and definition into the musculature. Right now everything is a bit on the round side
3: I elongated him mostly for style. You could also go the other way, making him shorter and more impish like the concept art.
Both can work. With fantasy stuff I'm of the opinion it's better to push a little too far in the dynamic range than be safely in the average. Also includes various changes to the abs, mainly trying to give them a more interesting shape, and have the ribcage underneath feel more present.
4: Colored him just to get a better sense of the end result. The skin palette itself is a bit high in saturation and value. Could use more range.
5: Just having fun here. A heavier line art style might be interesting.
6: He was a little cold without pants.
Hope this is of some use to you! Glad to hear you're getting back into art after a long break.
also, here's the reference I was using as I made this edit. The gnarly, skinny muscular type seems to be fitting for this sort of thing: