I've fixed the gem counting problem for levels before level 8. Also, the HUD is not drawn for level 8; place a 0xDB tile anywhere in the area8.map to force drawing of the HUD for that map. Conversely, place a 0xDA anywhere in a map to hide the HUD for that map. In addition to these tiles, there's also a 0xDC tile which forces the 7-8 gem warp to update according to how many gems the player has collected. This allows the player to collect all the gems on the last level and return to the 7-8 gem warp and eversion. In the original Eversion, you would need to restart the level in order for the 7-8 gem warp to update.
You can't reach these tiles normally, you'll have to turn off "Available tiles only" from the edit menu to get to them, or you can edit "./data/tileLayout.txt" and "./data/tiles.png" and add the 0xDA to 0xDC tiles manually. Closing all the windows in EversionEditor and then opening another window will force the reloading of tileLayout.txt and tiles.png.