sadley they do fight
i would recomend u research a fish mroe before buying them
especially since allmsot EVERY one knows males fihgt and every lfs says u can not keept hem togethor when u purchase them
that aside.
back when is tarted wiht betta's i had two in there own 1 gallon conatiners
beside each other.a nd with out thinking one jumped into the others container and i had two dead fish
because one kills the other but the survived most of the time dies from its wounds.
your bettas in reality could have lived there lifes in the 55. if it was HEAVILY planted.
but both of them would be in great strees nad have few fins left.
as for a container. i preffer 1 gallon per fish or plus
u can keep in less. but this requires more water changes
oh and btw i own around 30 betta's right now. and have two in the spawning tanks
oh and about the breeding thing. i have come to notice betta's woill not breed unless water surfaces are still or near to it. and the 3 females evne mommy would eat the eggs up quick