Hi John,

The problem was resolved during private conversation via email.
Here was the main solution - I wrote:

What I have done:
1/ Exploded all blocks in the drawing. Without this you cannot delete layers inside blocks, actually you can, but you need to edit each block in Block editor to erase all unnecessary layers
2/ Blocked layers you need to leave in the drawing
3/ Used ERASE command to erase everything from the drawing except on blocked layers
4/ Used PURGE command to purge all empty layers
5/ to solve the problem with DEFPOINTS layer, which cannot be purged (it is special layer and AutoCAD doesn’t allow to purge it), I used WBLOCK command with * option to write everything from the drawing to new file. DEFPOINTS layer now deleted too.

Maxim