As others have said go weigh your TV fully loaded with a full tank of fuel, all passengers, pets and gear you intend to have in it when towing. Take the scaled weight and subtract it from your TV gvwr to get your available payload. Take the scaled weight and subtract it from the tv gvwr to get your adjusted towing capacity. Also pay attention to what your receiver/hitch ratings are (there will be a load bearing and a weight distributing rating). You need to stay within all of these numbers. Tongue weight must be subtracted from payload also.
Next understand you will never tow a dry or empty trailer so dry tongue weight is useless. Loaded tongue weight should be 13-15% of the loaded trailer weight. Here is the trick you do not know how much weight you will be adding to your TT (on average people tend to add 1000-1500 lbs, some more, some less). with Not knowing these answers, calculating by trailer gvwr your safest bet.
Some have mentioned calculating backwards..... This means take your available payload and divide it by 15%. This will give you your max gvwr. Towing at max is not a fun experience and tends to incorporate a lot of white knuckle experienced. Honestly for the tt it sounds like you want, you would be well advised to upgrade the pathfinder to its big brother the armada. The armada is rated to tow 9100 lbs and rated for hitch rating of 910 lbs. Be forewarned, payload sucks. After 2 adults, 1 small (35 lb) child and a 70 lb dog my 04 armada only had 800 lbs of payload left for tongue weight. You can still get a heck of a tt with that kind of payload, just not a monster like mine. I suspect you will find a similar limitation on the pathfinder. Also you will find that 6 cylinder screaming on the hills (and possibly overheating).