? Treatment with Simultaneous Illnesses

We started dosing Spike last week Sunday with .5 unit of Lantus. He was doing well. His numbers were coming down, but we thought he would need to be increased to .75. We decided to dose at .5 for a week, then do a curve to get a better picture of how the insulin was reacting with him.
Around Tuesday night, into Wednesday, he started displaying his chronic allergic sinusitis/rhinitis. He is on azithromycin for mycolplasma daily. Cornell Vet advised he may need to take that indefinitely. He is on no other antibiotic. He will always have this condition.
Usually when he shows the sinus issues, we give him several vaporizer treatments over the course of 2 or 3 days. It usually improves his condition and he gets better. We have been doing that this week. Thursday he seemed very unwell.
We continued to test his numbers, feed him and dose him with .5 units. If you review his SS, you can see an increase in numbers.
We know that an infection or inflammation of some type in his system will increase his numbers. That being said, we're unsure if we should increase his insulin to .75 or let it ride until he fully comes out of this sinus issue.
Another problem. We are between Vets. We have an appointment with the new vet on 8/29. I have not advised the current vet of the change, so in a "major" pinch, we could see him. I also don't want to take him in the current vet if unnecessary, with the new appointment in 10 days. Spike gets very, very stressed at the vets, sometimes it throws him into a pancreatitis flare. (which I try everything to avoid the flares)
We are travelling on a slippery slope with Spike, trying to juggle his illnesses and doing the best to control them all. But I fear I may never get him into a possible remission with all the inflammatory and infections he does get/have. And you know, that's okay, as long as I can control him with insulin.
Any words of advice at this point? His SS can be found in signature line. Thanks.