But aleks don't worry the "30 fps rule" don't apply very much to traditional animation, yours should work very well in 18 fps, and inbetweening all of the keyframes is a HUGE task, but it doesn't have to be that way, if the animation feels right with just a few inbetweens then just leave it that way. Take this short for example
[link] this gal has an INCREDIBLE control on keyframes but she doesn't inbetween each and single movement. I recommend you "The animators survival kit" to learn more about keys and inbetweens, it changed my life... really!