I'm going to suggest you try one more thing.
Take those two fans you installed below the fins and install them in the baffle board by the upper vent, blowing outward.
My experience is... the fans when mounted in the location you have them, causes the air to pack in the upper part of the box and fights itself trying to get out the vent cover.
My fridge had three fans from the factory (where yours are currently mounted) and when they came on, hardly any air came out the upper vent.
I added one fan to my baffle in the right-most position (see attached modified photo of yours) with the option to add a second to the left of it if needed. I also added one fan horizontally by the lower vent cover to pull air in the bottom vent so the upper fan could blow it out. I wired them to the existing 12v on/off relay (with a switch so they could be turned off) but I simply leave them run anytime the fridge is on. I used good ball bearing fans and you never hear them. The three noisy/cheap factory fans never even come on anymore.
It works so well, I never added the second fan to the upper baffle.
With this set-up, it should exchange enough air that you should be able to have a piece of printer paper 'stick' to the lower vent (on the outside) when the fans are on.
No way would it exchange that much air previously.
Hope this helps. I don't have a photo of mine as it's been parked next to my garage with the slide out and I can't access it to get a photo. If you need me to, I will put the slide in and snap a couple pics.
Also get yourself one of the inner fridge fans like in the second photo to mount on the inside fins. Really helps. Buy them *HERE*