What a beautiful kitty you have. I dont post often but was concerned that you mentioned upping your kitties seizure meds. These are very powerful meds, with their own set of side effects as well. As others suggested, i would wait for the other results, and not up these meds, especially if they are not helping.
With regards to your kitty running around like a crazy cat for an hour or so, this is a young cat, my kitty still does this and she is 16 years.
As far as the back leg weakness, I wonder, did they do a hip and leg xray? I see reference to chest but nothing else, maybe i missed it.
Switching your cat over to canned is a wonderful idea, can only do good. Just make sure you do the switch slowly over seven days so as not to upset their tummy.
Lastly, please keep us posted on how they are doing.