2.2.5 and i started to set it at frame delay = 5, shrink frames by 2, merge is off, crop is on and palette is on.
well i've never used 2.25 and honestly they're version of determining framerates was strange. Also this is 2.25 which is a mod of 2.5 and 3 and probably a broken mod.
You should really just use pivot 3. The frame rate you have your pivot at in your .piv file will be what the .gif saves it as.
Also, you shrunk it by 2 and the size is still around 506x415? dude make your animation surface smaller. Thats way too big, if not shrink it by 3 or 4, thats way too much white space for it to need to be that big. Might improve your frame rate consistency aswell. A smaller .gif also "blurs"(cant think of a real word), minor easing mistakes so it'll actually look better in the long run.