The wall vent takes air in, the heat exhausts through the roof vent. That being said unless you used an articulating bracket with arm to keep the TV away from the vent, you would be taking a chance of restricting the airflow, which would cause inefficient cooling. That takes you to the next issue. The vent cover is thin plastic and the top is held in place by two small tabs that slide into two holes. Its possibly the weight of the TV would eventually deflect the cover enough for those tabs to disengage, then your 32" TV will be on the ground.
Find the studs. It can't be that hard on a stick and tin trailer. Have you tried looking at the side on a cool morning when the side has condensation on it? You should be able to see every stud at the low flats of the siding profile as those areas will not have the condensation.
I can't imagine that by pushing firmly on the low flats of the profile you can not feel the stud locations. I highly doubt Dutchmen uses siding any thicker than .024 which is almost foil.