Personally I'd would have offered to take the snake they're scared of off their hands for free. They obviously don't give a crap about its care and considering the costs of building a new viv and getting the poor thing mite free, they wouldn't have got much cash from me..
However it's done and well done for doing the best you can

. With the aggression it's all about patience and time, start with short sessions of about ten minutes when there isn't people walkin past and around you as this obviously freaks him out. Also try not to approach him from above as this will scare him due to natural instincts of predators coming from above..
Goodluck with him and please keep us updated on how he does. Oh an where's a photo of limbo