To me, any hint of ammonia smell means you need to add more litter. That always took care of it for me, when I was first starting out. I've never used anything other than shavings in the coop, unless I needed to add DE for a mite problem, and haven't had a problem with smell. We've never used any fans, but did add windows for the hot, humid summers here.
I don't know how others do it, but for DLM I add litter a lot more frequently than once a month. I don't add a lot at one time, just a light scattering over the top where it looks like it needs it, like under roosts or any other more heavily pooped in area. This is more like every few days. I like to keep a feed scoop in the top of the litter container, in the corner.
I've also never raked the litter. I guess that would be effected by your square footage per hen. I really like 5 sq. ft. per hen. I've read that at 4 sq. ft. per hen, you get a little poop crusting on the surface that needs to be broken up and mixed in a couple of times a week, at 3 you get more and at 5 you don't have any. I wish I could remember where I read that!
Anyway, sometimes it just takes a little while to get the hang of managing a particular coop. I suspect there are multiple ways to do DLM, just like anything else. You might want to try the light sprinkle more frequently method.