Sounds like you have Cox Communications for internet; me too, similar speeds. I can reliably stream 720P 25 FPS (YooToob) but 1080P is very hit/miss. I suggest the internet provider be consulted and see if they'll bump the up speed to 20mbps. I called Cox and they bumped my down speed to 150mpbs at no extra charge. I guess nobody else with a residential account needs up speed?
Almost all internet services have upload speeds as an afterthought.
You should have 1.5 to 2 times the upload speed as your stream.
15 to 20 mbs is probably the minimum for a decent 1080 stream.
BTW a high quality 720 feed is better than a low quality 1080.
Some streamers, like the ATEM mini, have several different upload bit rates at each resolution.