keep the tires and invest money in a TPMS. Between the neighbor and I we have logged over 250K miles on trailers with no failures. He uses whatever he can find for tires.
TPMS has saved both of us possible blowouts by letting us KNOW IN ADVANCE we had a SLOW LEAK. FAST enough to not catch it between rest stops, but still a slow leak.
One doesn't know of a slow leak till to late when it blows. you won't feel a trailer tire going down till it blows.
Our opinion (and based on experience) is that the majority of blowouts are caused by a small puncture that one doesn't catch till it blows, not by a instant catastrophic failure.