Always good to acknowledge when something isn't turning out right and looking for a different option. Never easy, but always a learning experience
I use Fiberglass window screening to put on top of the egg crate. You can buy it by the roll at Lowes or Home Depot for cheap (I think for like $4 or $5). Just cut it so it is 2 or 3 inches bigger on all sides so the substrate sits in it like a bowl and you will be all set.
Did you get a digital Hydrometer? Analog ones are notoriously inaccurate. Heck digital ones are not all that accurate. I ended up buying a couple and running them side by side to see what the variance was so I could guestimate the actual unity.
Tnak is looking good though, keep the updates coming!