Can I assume that you can adjust the focal length with that clamp that's about 10" up from the dish?
The dish mesh looks OK to me, that should work fine on Ku unless the dish is warped. The big question I have is getting the feedhorn at the proper FL. I would check to make sure that the feedhorn is centered fairly well, and if so, find a C-band sat, and try to peak that sat by moving the dish in all directions. THEN, try to peak the focal length adjustment by moving the whole buttonhook thing in and out. Once you're fairly close, try to peak the focal length on a Ku sat, again by first tweaking the aim in all directions, then by tweaking the focal length.
Reason for the 2 step process is that if the focal length is off quite a bit, that Ku won't focus at the same point that C-band does, so you need to get the focal length pretty close before trying to peak on Ku. The problem I see with this dish, is that it looks like there isn't any convenient way to change the focal length of that buttonhook except from that clamp you have 10" up from the dish, and that's hard to get to when you're aimed at a sat. Hopefully there is another way to adjust the FL that I"m not seeing.
If you try some of the previous suggestions related to centering the feedhorn, I would recommend getting the focal length set first, because if you start running cables to the feed, then you might not be able to adjust the focal length, as it doesn't look like you have much room for adjustment where that clamp attaches.
The advantage of a buttonhook like that is that you can usually adjust the feed in and out easily to get the proper FL without altering the F/D setting on the feedhorn. The feeds that are mounted on 3 or 4 arms are more stable relative to centering, however they really make it hard to change the focal length without changing the F/D setting on the feedhorn. I can't tell if your feedhorn has an F/D adjustment or not, but I assume that it must.
But anyway, unless you have that feed pretty close to the proper focal length, then C and Ku won't focus at the same point, because C will be a blurry spot, while Ku will be a donut, ie not peaking at the center. But as you correct the focal length, that donut focus turns into a spot that's centered at the same point that C band is focused. So if you intend to do both C and Ku, then you need to be pretty close to the proper focal length, and you really have to adjust C band first, then Ku. If you try aiming on Ku first, you'll be peaking on an off centered ring of the donut. (Hope that makes sense.) Hopefully there is some way to adjust focal length without getting all the way up to that clamp that's 10" from the dish surface.