1) To be sure you have enough load carrying capacity in the tires, you need to have individual tire weights because there is front/rear and side to side variation. IMHO, you need a 15% over capacity. It appears you barely have that. So I would suggest a test: Pressure buildup:
You want no more than 10% - excluding the ambient temperature effect (2% for every 10°F).
2) Those tire load tables are MINIMUMS!! You want to be over that! Since tire wear is not an issue on a trailer, a bit of over inflation doesn't yield much in the way of penalties.
3) Wheels are not required to have max load or max pressure written on them (unlike tires!). That's probably because there isn't an issue with wheel failures. The best information I have gathered from wheel designers is that inflation pressure is not the issue with wheels, but load is.