Tongue weight for a conventional TT {Toy haulers are whole different animal due to the extreme rear loading and should have even greater tongue weight} should be approximately 13 percent. Significantly less will cause or at least exacerbate sway which is to be avoided at all costs.
When computing your tongue weight ignore any reference to dry weights as they are worse than useless {see also "dangerous"}. Also, ignore the dry weight of the TT, instead use the TT's GVWR which will be far more accurate than any dry weight.
Simply put, get the rig weighed, adjust the psi of your tires accordingly and compute your towing weights from there. Chances are good that you will never be able to tow anywhere near your TV's rated "towing capacity {another nearly useless number} as you will run out of {TV} payload long before you reach the alleged towing capacity.
Adding a weight distribution hitch does not change your tongue weight numbers or hitch limits except that you now have an additional 100# to add to the equation. Properly set up they transfer {distribute} some of the weight from the rear axle onto the front axle of the TV.
:C