I don't remember any large seal on the face of the recirc door, maybe just a foam type edging around the perimeter.
I'm not sure the fan speed has any relation to the compressor at all in terms of the lenght of cycle of the compressor. Indirectly it will affect the delivery speed of the cool air and therefore indirectly may shorten the time before the temp sensor sees what it is looking for as a match between requested temp and temp achieved. I do think that the higher fan speed may be drawing in a larger quantity of hot air while the compressor is off line than if the fan were running at a lower setting.
Seems like my old 240 had a time limit that the compressor would stay active. I think there was a warning note not to run it at "max" for maybe five minutes or so. I thought it overrode the temp sensor and just kept the compressor on steady til you felt the worst of the heat had been extracted and then you could turn it back into the "normal" range where the temp sensor determined the cycle lenght. Your problem of the compressor staying off for five minutes may be a protective cycle it goes into when it is unable to satisfy your temp sensor, and I would suspect, as the other poster mentioned, that low pressure/quantity of freon or r34 is the real culprit. I think my wallet would bet on that direction.