For cables Hart Audio is a popular nice cable. For $70-ish you can get the headphone cable plus several attachments for balanced XLR, 1/4", 3.5mm etc. so one cable can be used for different connections. You can also customize the color if you want.
One trick for clamp force is put the headphone around the back of a couch or chair overnight. May not work for all bands but sometimes it works.
The Sundaras have separate connections for left and right so both sides will have to be connected to hear sound in both sides. I’m not familiar with ModMic so I don’t have anything more specific. You might try the gaming thread and see if anyone can help.