Thanks everyone. I really do appreciate all the support. It helps me know I'm not alone in this.
Since you all asked, here are
Miko's Numbers.
And Barb, I believe you asked how old he is...Miko is 13.5.
According to Dr. Shelli and my vet, everything looks well (for a kidney dog). Yes, things are off, but well, Miko has kidney failure, so numbers will never look right anymore.

Poor guy. She felt the ALt number could be high for various reasons and suggested a couple of things to get the BUN numbers down. Otherwise, everything is okay.
Now, as I told her, I wish my vet would explain things to me like she did. I probably wouldn't have freaked out about the high ALT number and what it could possibly mean (liver issues). So, I decided to do the following:
1. keep my appointment with the internist (specialist). It will be 1 month after my last blood/urine tests, so most likely she'll want me to redo them to check on the liver numbers again, which is fine.
2. if she gives me the same diagnosis of my vet and says my vet is doing fine, I will stay with my vet, but ask him to explain the
bolded numbers on the test results (bold means out of range), in a better way. If he explained them like Dr. Shelli did, I probably wouldn't have freaked out, however, he doesn't know me well enough to know I need that kind of explanation, so I'll ask him for it. If he gives it to me, great. We're all good then.
and 3. if the specialist gives me something else, I'll have to decide what to do then.
I think the hard part is knowing when something is completely off, even when he acts normal. I mean, the only sign something was going on with Miko was that he was drinking a lot more water. And once every 6 months, having an accident in the house (if that). It makes you question if it really is kidney failure, and what else could be going on that I don't physically see.