Hmm... okay, for starters, regarding your cooling... you are losing significant air flow to that "draping along the wall" pattern... the air is working up and over ach of those drapes, and it is slowing your air flow. Fixing this could result in an increase of air flow and you might be able to skip the insulation. Honestly, if you are right about the heat exchanging on it's way through your ducting, then correcting the air flow would probably help more than insulating it.
Keep in mind that ducting is not a heat sink... it will exchange some heat, granted, but the faster the air moves, and the more direct the air path, the less time the air has a chance to exchange through the wall, and less push against the ducting directly from it hitting the bends.
My advice would be to take the duct off the hooks and just run it along the floor, in that bottom corner, which will keep all bends out of it, since floors are nice and flat and evenly supported. Either that, or tighten up all the duct runs so that they are pulled taught.
Finally... I can't tell what is going on with your intake end... it looks like you have an intake coming in from outside the room, running into your hood in kind of a weird way that hits the corner of it rather than the intake duct...? What is going on there? I can see the intake duct sticking off behind it... are you using a Y splitter so that you can draw air from outside as well as in the room or something? If so you are diminishing effectivity more...
My advice would be to either get a second inline fan set up to exhaust the room, or use a passive intake to provide fresh air to the whole space, and then draw the air from the room, through the hood, and out. That way the cool air is flowing into the room and becoming available everywhere it's needed, both to cool the lights, and to provide fresh air to your room...
But I am getting ahead of myself... can you explain your ducting on the intake side?