Lightmapping a highly sharp mesh?

In lieu of my modeling skills, I’ve been playing around with a voxel/cube art style. I’m having a few issues with lighting and texturing, however.

How in the world should I unwrap these meshes for lightmaps?

This looks alright, however there are quite a few artifacts, namely the dark splotches near the ceiling joists and the back of the wall (not shown). The mesh has 19000+ vertices. I exported it from MagicaVoxel with a custom exporter. It’s literally a mesh with verts for every quad. After remodeling this mesh (down to 800 vertices) and making a proper lightmap (64x64), I got this result (still with a few edge bleeds):

Some detail views:

So what should I do? How should I organize the UVs without using a ridiculously huge lightmap?

I really don’t have a good workflow. Does anybody know how to make this work?

It’s hard to tell without seeing the UV’s, issue with that type of thing is that you have to create a lot of seams in the UV’s to be able to flatten it out. The top of the beams are the main problem because of all of the corners, it’ll be a big hassle to split it minimally.