There is no way to change the ATEM 1/ME to 1080p - that's only possible with the 4K models.
However - I think I may have misunderstood what your issue is. Is your issue purely with using those adaptors to convert HDMI to Cat5 and get your program/multiview sent 100ft away to another TV?
In the end the some HDMI to Cat5 extenders really just don't work all that well with the ATEM's. I have not heard of your model before... so I cannot tell what may be going on. There are many reports of HDMI to Cat5/6 adaptors that do work with the ATEM. You may need to search the
ATEMUser.com web site to find the ones that people have found worked (although mostly I recall these being uses for camera INPUT - not for the multiview out).