A little late but I hope you are still searching for an answer or I am wasting what little knowledge that I have....
I don't quite understand why they are telling you to use a blade rated at 5000rpm. The normal recommendation for all saws is to NEVER use a blade rated at a lower than motor speed. The reason is that you would end up looking like the victim of a ninja warrior, with pieces of metal flung through your body. The blade will disintegrate at higher than rated speeds. I even looked in the instruction manual I still have for a Sears 10" radial saw and it tells me to only use blades rated higher than 3450rpm. In fact, if you look on the dado and normal blades, they should also give you a "not to exceed rpm". As long as you follow the above everything should be fine.

One word of caution regarding the dado blade. Follow the instructions carefully. The more you use it the more cocky you become- and careless. You cannot believe how fast that piece of wood can travel once the blades grab it the wrong way. Good luck.........