Thats great to hear! Sounds like hes starting to get there.
I always used blankets with the grobags.. even though they say not to. I think its just so they dont overheat. But in times like summer, when id put my kids to bed it would still be really warm, but come night time it would get cold so id put a blanket on them before i went to bed. Its the same now. It gets colder at night, so in order to comply with their guide, they would be sweating when you put them to bed to start with.

Hope he keeps it up and keeps getting better for you