If I recall right the maximum seating capacity on SK
736 is 112 seats... however, most of those are convertible seats as you can change the seating configuration from 3+3 abreast to 2+3 abreast by just pushing the button under the seat. Obviously, Business class has this 2+3 configuration... Configuration is changed after every flight depending how many business vs. ecomony class passengers there will be on each flight. For some reason which I don't know, B737-700s don't have these convertible seats so seating capacity is always same.
B737-600 has two lavatories and one is located in the front galley and other is in the back galley. The front lavatory is for business class passengers and it is more roomy with better facilities as well (wooden toilet seat + window). I don't know what is the maximum amount of passengers per each toilet, but obviously in B737-600 with very small business class there is a lot of economy passengers who have to share just one toilet... Not very nice when that is inoperative.