Especially every turn / curve accelerating or decelerating that 7k trailer & tongue weight is causing some tire scrub, so itís normal. Highest tread wear rating / warranty will last the longest but may not be suitable for your use in Alaska.
Best wear & max stability / load carrying capacity is at less than max sidewall psi rating. (Many people assume itís at max sideways psi rating) The Mfg and or a really good knowledgeable tire retailer can look it up or find out what psi max load capacity is at and thatís where you well get the best tire life. (But not necessarily the max mpg)
On an SL standard load or P passenger tire like our OEMs is often 5 psi below the 44 psi max inflation. On XL load rating this is often about 6 or 7 psi less than the 50 psi max inflation rating. You probably have E loads and Iím sure they are different. The tire Mfg customer help or their retailer should be able to find this but bargain brands & foreign Mfgs donít always make finding this easy. In the end you figure out what works best by closely watching wear anyway. Outside temps and road surface also matter so.