We really no longer recommend oleander in any form for cats - their systems just cannot handle it from virturally every report we have had. I have no personal or anecdotal experience with bloodroot and cats, but see from a Google search that it has been used - perhaps diluted quite a bit as it is pretty intense stuff. Here is one discussion thread I found:
Colloidal silver has worked very well in combination with inositol/IP6 in many different animals - and it often results in renewed vigor. You might also consider painting the tumor with iodine and baking soda (alternating back and forth) and another item to consider is diluted DMSO. As far as I can tell, ioding, baking soda and DMSO have all been used medicinally for cats.
I hope that helps!
I can see your delimna, but I would think you have to try something. The DMSO is a super penetrant and anything you add it do will very quickly penetrate into the tumor. Maybe try it with different things - iodine, baking soda, black salve?? Sorry to say, but it is really guesswork here, as surely you must know.
Whatever DMSO he gets down will also help with absorpiton of whatever else you are giving him. Insofar as the amount of colloidal silver, I don't think you can give too much up to the limit of what he will drink/tolerate. I have mixed it 50/50 with dogs drinking water before for many days in a row after a rabid skunk attack.