Path from 3rd to 4th spawn point is a tough one.
The heal may have bug - it sometimes stuck after first use. Game restart may help with that (progress should be saved). Sorry about that.
Did you use the Compiler? Some people miss it - I failed to make a good tutorial for it. Just stand on respawn point, press "ESC" and click on "Compiler" menu item. You can spend bits to buy health and ammo. You can farm bits by killing any bots.