Overwhelmed and worried about safety

You are on the right track figuring it all out. In the end it’s all what the manufacturer says. For a tt max tow rate is never the number you should look at for what you can tow like you already figured out. If you are under everything you should be good to go but there are so many other variables and the closer to the max the less enjoyable the tow will be. Some people have a higher tolerance for sway and all the pushing and pulling that goes along with towing. Others don’t like it at all, that is camp i fall in. In the end my totally uneducated opion says that setup does not sound ideal but if the numbers work you should be good to go.