The only reason to use thyro-l long term is if thyroid function is low. It does not help to control insulin and any weight-loss effects are only temporary until the thyroid compensates for the excess being delivered by down-regulating production. If his diet has been mineral balanced, and with the PPID/IR controlled, any low thyroid result will likely correct itself as the thyroid is supplied with the needed nutritional support. If he was mine, I'd be speaking to my vet about weaning off the supplementation.
Essentially, he's had no change in his insulin level as the original 12.89uIU/ml was a fasting result (falsely lower result) while the recent 18.37uIU/ml was done non-fasting and during the fall seasonal rise. ACTH crept up a bit due to the seasonal rise but not to an alarming level, so your vet's advice seems reasonable regarding raising the pergolide (Prascend) dose some.
You need to upload the EMS calculator results to your case history manually.
Lavinia, George Too, Calvin (PPID) and Dinky (PPID/IR)
Nappi, George and Dante Over the Bridge
Jan 05, RI