that is a little bit of a problem now.. have you weighed the trailer? people can say all they want but until you know the exact weight of the trailer you can't know if that 950 is ok. we can guess, my guess would be maybe. I personally don't like the small 12" tires and wouldn't run anything under a 14" but that's just me. the other issue you can run into with bigger tires is if they will rub on bumps or when loaded. those tires are rated for just under 1000lbs, I think the brand that popped up first was 990lbs at 90 PSI, so if that 750 was on the tire you could probably just get a different brand the ones that popped up here were Sutong Hi-Run trailer tires in that size
To start, I would drive to the scale with your trailer, unhook it and weigh your front and rear truck axels (individually) then hook back up, get the measurements for the front (won't change most likely) the truck rear (should see an increase) and the trailer axel its self. add the increase on the rear axel to the trailer axel and that will give you the total weight of the trailer.. then you have to find out if that 2000lbs is a GVWR rating or a cargo capacity, if it is a cargo capacity you have to find the GVWR rating and subtract the actual trailer weight you got at the scales and that will give you your true cargo capacity