It's safe to continue the metformin. It's not doing anything for his insulin but may well be helping with pain.  I'd continue it.

There have been no formal safety studies on acetaminophen. I worry more with ponies because they are at high risk of fatty liver with EMS and that increases the risk of liver damage from the drug https://pubmed.ncbi.nlm.nih.gov/31307592/ . It's probably not doing much anyway. Try stopping the evening dose first and if he still seems the same, stop the morning dose too.

That LF toe looks much better.

The worst thing about that hay is the high iron but it can be balanced.
--
Eleanor in PA

www.drkellon.com 
EC Owner 2001