Congratulation on your new PR and very nice splits! The 48 min 10K is a great sign for a sub-4 in the future. I think if you can avoid a bathroom break and maybe build your endurance with more miles (peak of 40mpw seems low - but I agree you don’t need 20milers, just run more overall) you should be able to improve a lot!
Thankful that I’m fit and healthy enough to still run at age 60.
Thankful that my husband has taken up golf, so I no longer feel guilty about going on long runs by myself.