1) You don't need extreme amounts of weight. To be completely honest, anything more than 3 pounds isn't going to help much as you're not going to be wearing more than a 4 oz glove if you actually fight. Also, you are using the extra weight to build speed and muscle endurance. Anything else will promote the growth of mass, which isn't necessarily a good thing.
Would 15 to 20 pound dumbbells be a problem then?