you could open up the wall like this, so that if someone spams the point from there, he cant hide behind wall or unbroken window. this would make the 2nd floor counterspammable and snipable
here you could try putting an extra exit, although it it stays open, it'd probably make the spawn more spammable. widen the path like shown so there's more space to dodge incoming spam
you could just make spawndoors close instead of staying open.
widen this area too. make it so that when theres spam, players have enough space to avoid it, instead of being forced to either stand back or run straight at the spammer
if you dont want to use doors, dont use them. opening this house up would also allow for a sentryspot there without using barrels that received some objections in impromptu
you said setting props to have no collision sounds like work. actually all you have to do is use entity report as shown and then set collision to nonsolid for all props at once
this health and ammo seems to be too far from blu spawn to help attackers and too far from cap point to help defenders at cap point. i believe it only helps the spammers and you should remove it.
put a stronger supports there sometime
sort out your skybrushes here. that tower and some surfaces near it keep popping in and out of view. you might want to move that tower into 3dsky like in gravelpit
you could try putting a building here that faces the point and put full ammo in there to help engies setup some defense quickly. then if it works ok, expand it somehow - make a ramp up there, 2 stories, badlands spire, quaddamage mid, something, anything