How to make DIF files smaller?

My game doesn't use dynamic lights or any lights at all, just some fake textures that make it look like the level is lite up.

My main concern is Framerate. I did all I could: Portals, Detail brushes, optimizing geometry to use less Brushes etc.

So I've got a few questions about the DIF format...

1) Is there any way to export the MAP 2 DIF WITHOUT lightmaps? I believe the DIF file would be smaller if it didn't include any lightmap information. Since I don't use actual lights in my game and those are faked with textures, I don't really need the lightmaps. Is there a way to achieve this?

2)In regards to DIF and DTS files...I want to make decorations by trimming a wall and I have two choices,I can either use a single brush wall and a DTS plane on it OR I can split the MAP wall into two brushes... which one of these scenarios would be less intensive for framerate?

Thank you all in advance!