Sounds like
Meta menardi from the egg-sac description alright. Spiders are very adaptable and resourceful and will make the most of habitats or move to more suitable habitats.
M. menardi have a specific conditions and habitat as you'll be aware, so you may find them moving on. I think anything you do to accommodate them is admirable but I'd not worry too much, it's hard to replicate their required conditions as you need the right balance of dampness and airflow
.
No.9 Spider