It looks like you got a good recommendation on how to remove the grips but don't use vice grips. You could accidentally crush the poles if you're not careful. Also, you want to avoid gouging the carbon fiber - I would use the hot water method.
To cut the tube, wrap tape around and cut using a Dremel cutoff wheel if you have one or a hacksaw. Don't breathe in any carbon dust. Apply some CA (cyanoacrylate aka superglue) to the cut ends and let it dry.
Depending on the fit, you may not need any glue to keep the grips on. See if you can slide them on with water; they may stay when the water dries. If you use glue, don't plan on ever getting them off in one piece again.