Re: should I worry?
I would put in a request for the hydration. Do you see a nephrologist and can you get him/her to ask for it? You can cite the fluctuating eGFR as a reason. As for the rise, this can happen for many reasons including a decrease in exercise and an increase in hydration. GFR is calculated based on your creatinine and estimated size. So it's not always that accurate.
If you can't get the iv, spend the couple of days previous to the procedure working on stuffing yourself with non-caffeinated fluids. Hope this helps a bit. Don't worry too much about the dye. If you are not too susceptible, it won't affect you anyway, and if you are, your function is still most likely good enough to keep you safe. Sorry I can't be more specific than that, but these things are always a risk.
Dxd T1 1966, 2001 dialysis, 2002 kidney transplant, 2003 insulin pump, 2008 pancreas transplant