I've updated the ZIP with the grids in it to include the one you were originally asking for. Sorry about that.
As for Owlbear, I recommend using the Diametric Assets instead of the isometric assets. The other suggestion I have is to hold the Ctrl key when moving things around to avoid the snapping. As for the other issues, there is really not much I can do to support Owlbear users because it's not designed for this perspective. If you are wanting the highest degree of control from your map design, it might be best to use a program like Photoshop or GIMP to arrange large chunks of your maps as PNG files, then bring those into the VTT.
Let me know if this helps!