i would say if its broken it needs to be returned and refund given as it was new and will need to go back to manufactor
tell them if they choose to keep it you will still need proof of the damage as item was sold in good and new condition
they may have broken it them selves by accident
tell them you have proof via photo that it was not broken when you sold it and unsure how it could of broken when packed so well so if they can return it to you then you will refund them there money
as for pushchair
e mail again explaining your situation tell them you paid for 48 hr delivery
if it turns up as staed paid for 48 hr delivery it will be posts problem not theres
e mail again later if havent heard back and say you will have to make a paypal dispute if not heard back by tonight as you are really in need of a pushchair