I'm so sorry that I was off my computer when you posted your concerns about Dolly; my apologies for taking so long to get back to you.
It certainly sounds as if you're doing all that you can to keep her healthy.
I have several thoughts/comments about what you've said about her.
1. As I'm sure your vet has told you, it take about 70% of kidney tissue to be damaged before we start to see an appreciable increase in BUN and Creatinine and this is irreversible damage. These values can also influenced by other things such as body condition and whether or not the patient was fasted first.
There is a new test here in the States, called SMDA, which is not affected in any way by other parameters and is specific to the kidneys only. It's also an earlier marker for this problem and can be elevated when only 20-40% of damage has been done.
What we're also looking for are changes in all of the values we monitor an upward trend, in other words, even though those values may be within a normal range. This is particularly true for Creatinine.
I'm not trying to add additional concerns or worries, you understand, but just wanted to provide information which, hopefully, you've already been told and I'm just repeating it. If not, then at least you're aware.
2. I absolutely agree that stress can be a trigger for a lot of conditions and can exacerbate existing one; it's best to be avoided if at all possible.
3. I think the behavior you've described when she's outside may be something similar to marking behavior in dogs although she may have mild FIC as well. If this is Idiopathic FIC (the most common kind), then symptoms may appear intermittently and then resolve on it's own. As you probably know, stress can definitely trigger this condition in some cats so I think the Feliway was a wise move.
4. I think a urinalysis isn't a bad thing to do, under the circumstances, if you can manage to collect it without having her seen....sometimes easier said than done!
5. I would increase her water consumption if you can. One thing to consider would be an indoor water fountain which many cats really enjoy. If you're not currently feeding her wet/canned food, then I'd consider this as well since the #1 ingredient is water.
Some of these cats will respond well to Cosequin for Cats which is available online, at least here in the States. This product was originally designed as a joint supplement but it was found to help some feline patients with FIC. Since it's so safe, I often suggest it for my patients with this issue.
I hope this helps, although, again, my apologies for the delayed reply. Deb