Here is some useful information I picked up from a grow book by Gorge Cervantes
" Vent fans are usually attached to ducting to direct air out of the grow room. Flexible ducting is easier to use than rigid ducting. Keep the ducting straight and short. Long runs of ducting cause less air to be expelled and at a slower rate. When ducting turns more than 30 degrees, air movement declines and less air exits the other end. Ducting at no angle moves the most air. Ducting at a 90 degree angle moves the least air."
I saw in your first picture that the exit exhaust Ducting is at a straight 90 degree turn. If I had to guess your fan is not moving any air at all, or very little so your 1000w HPS bulb is getting some serious heat buildup. I hops this helped.
Peace and positive energy to you.