Hi there, sorry about the diagnosis. It's probably feeling a bit overwhelming at the moment.

Vets used to be taught (heck still are in a discussion I had with a vet student last week), that acromegaly is rather rare. Recent research shows that in fact one in four diabetic cats has acromegaly. Here is a post with
lots of articles on acromegaly if you like to read. Feel free to fire away questions, there are a few of us here.
Some first comments - you may want to consider switching Levemir insulin at some point. It doesn't have the acid base of Lantus, which seems to sting some cats, especially at higher doses. Neko didn't have a problem with Lantus and got to 8.75U on it, but she's more even on Levemir so I think it's better for both of us.
Where are you located? There are a few options for treatment in North America. In addition to Stereostatic Radiation Therapy (SRT), also called CyberKnife, the new option is hypophysectomy, or surgical removal of the pituitary, but it's only available in LA and Pullman, WA that I know of. It's more expensive than SRT - but might be a better option given your circumstances. The effects of SRT are not predictable in terms of timing, as the radiation neuters the tumor cells so you don't know exactly when they are going to die off. Without being able to home blood test, this might not be safe as you can get rather sudden drops in needs for insulin. The action of hypophysectomy is more predictable. If you want to learn more about SRT, Julie documented her
Punkin's SRT Journey. I have found a few articles on hypophysectomy (which wasn't available when we got our diagnosis), and am planning to update the post with the articles once I get them organized. And there are some more stories of SRT in the
high dose forum here - that one is pretty much info only, little postings.
As far as being eligible for SRT, you don't need another expensive CT scan - we didn't have one before we went to Colorado State University. Nor did we have an X-ray. It is useful to know the state of his heart with an echocardiogram, though we didn't do that either. I did one later when her heart murmur showed up.
Hunger crazies - got experience with that too! Several small meals in the first half of the cycle and the autofeeder helped save me there. Once her friend Otto (feeder) is on the floor, she stopped bugging me. When the effects of SRT started shrinking the tumor, the crazies went away too. She's still a good eater, but it doesn't drive me crazy anymore.
Neko was also diagnosed with IAA (insulin auto antibodies) - another high dose condition, but fortunately it has gone away over time. Did your vet ever mention getting tested with that?
Sorry for the novel - but I hope it's helpful. I know I dove into research as soon as I got Neko's positive diagnosis.