Glad to hear that the temps are sorted, but if you are losing that many seeds, something else is seriously wrong. How old are the seeds, and how were they stored? Definitely watch the excess water, but I doubt that that mistake would have resulted in the size of problem you have. If I were you, I would study the Cocoforcannabis germination suggestions and follow them to the letter with a few seeds to see it they do better. As the site suggests, you might try planting the tap rooted seeds in starter peat plugs or rapid rooters to see if they do better in them rather than directly into your soil.
I'm sorry that I can't help with the humidification issue, I just manually refill mine daily. It is inside my 4x4, so a different problem than yours.
Good luck with it.