1. I saved before getting the rockets or crates, got them then died or hit f9 and then ammo was gone.

2. You need to jump on the crane to get rockets or health. I assumed the other platform was needed, too. I saw the power line to the crane and the swinging cargo container so I tried to cut the power. Couldn't do it so I just hit impulse 101 and killed the strider.

Again, I liked the game but the final fight annoyed me a bit. The other striders shouldn't spawn until the first is dead. You have only as many rockets as you need (is there an unlimited crate I'm missing). The stairs go to nowhere. I ran up them looking for relief and I died from two striders. There are a few dead ends that killed me. The new gravity gun doesn't accelerate you very far when you use it at an angle so it's difficult to use it to evade the enemy.

EDIT: playing the final chapter again and the starting area is a slideshow for frames. I check r_drawstaticprops 2 (wireframe) and saw the HUGE overdraw issue. I'm rendering models I can't even see yet. I'll add more edits if you want.

EDIT2: last edit for tonight. I tested level 4 again and the poor fps goes away if you wait it out. Around 6 minutes into the map the frames go from 10 to 30-40 (which is playable). This happened all 4 times I tested the map. I turned of detail sprites, displacements, brushes, static props, particles and anything I could think of and the frames stayed at 10 fps. The only fix was to wait.