Just don't use accelerate if you have such problems with it, I've never used it.
i = ang(target_tilt - camera.tilt)*0.25;
camera_tilt_speed = minv(camera_tilt_speed+0.25*time_step,minv(abs(i),5));
camera.tilt += clamp(i,-camera_tilt_speed,camera_tilt_speed)*time_step;
Works fine, I've tested it now.
The other examples from my previous post work, too, and framerate independent (at least as long as fps >= 16).