The elements within a Block being on Layer-0 thing: Yes, that is the generally accepted and recommended method of handling Blocks.
I even go through the extra effort to locate and orient the Block (the contents of the Block) such that the Reference Point, and the Block's Insertion Reference Point, are at World coordinates X=0,Y=0,Z=0, oriented along the X axis (the Blocks Palette preview would be a "top view" of the window, door, etc.)
I'm with Nikki-- I think you should stick with using Walls. Draw your other extrusions adjacent to the Walls, if you'd like.
If you do decide not to heed that advice, I suggest you try using Double Lines. Pre-assign a Thickness (height) to a Double-Line via its Properties/3D page, that correlates with the height desired.
Using Properties Values Presets, you can have a number of these pre-assigned Double-Lines-- such as "4"x8' Walls", " ½"x8'Drywall ", " 4"x3' Brick Wainscoting",... you get the idea.
I still think you need to stick with using the Wall Tool. But if you go with Double-Lines, you can use the Meet 2 Lines and T-Meet Double Lines, Intersect Double-Lines modifiers to clean things up in hurry. (you can also do so with actual TC Walls-- at least in my ancient versions we can)
« Last Edit: January 13, 2018, 07:45:32 AM by Alvin Gregorio »
(mostly Residential Architectural 2D; no formal CAD Training; intermittent TurboCAD user since yr. 2000 [ver6.5])
---TurboCAD: V20.2PP(57.0)[as of 3/12/15]; V19DL(54.2); V11.2Pro; Windows-7-Pro/64-bit; Intel-Core-i3 CPU; 2.27ghz; 4GB RAM; Intel HD Graphics (CPU based)