That's some crazy looking tire, huh? Looks like the damage is repairable. Glad you got stopped safely.
The subject of poor tire quality is endless and for good reason.
Many trailer tires are being pushed right to their limits on a good day. Combined with under inflation, excessive sidewall abuse in jack-knife situations and excessive speed and there's not much room for safety.
Anyone who is pushing weight limits that may be worried about tire issues should bite the bullet and upgrade to 17.5 tires. They certainly are overkill in the weight capacity department for most but the heaviest of fivers, however, its very rare you see a post from someone running them with any issues. Not that you should tow at 75mph, but they are speed rated for 75mph, not 65 like most.
In addition, the 17.5 tires are available from several manufacturers like Toyo, Continental, Hankook and others.
Until Goodyear introduced their Endurance line (which has yet to be proven), the best 16" heavy duty trailer tire has been the GY G614. Overall, it has a decent rating but some have had issues with them, too.
Just my 2 cents. I have had the Goodyear g114 17.5 on my 15k+ fiver for nearly 4 years and 15k miles and they still look new - even the tread.
Safe travels.