cichlids are typically very territorial, so i wonder if a twenty-nine gallon tank that is also full with other fish will be enough space for a krisbensis, even though it is one of the more peaceful cichlids.
my platties are really mean to each other and my other species, but i've never had experience with swordtails specifically. it might be a mistake on my part, so you might have more luck/knowledge.
with rainbow sharks, i think a lot depends in individual personality and if the shark will accept living with barbs. i doubt they will because sharks typically eat anything small enough to fit into their mouths and although rainbow sharks only grow six inches, they might pick on your barbs when full grown. also, rainbow sharks need a lot of space because they're very territorial and what i have read says they like setting up several territories and will attack anything that invades.