In theory you could have put the bed in a different room but you changed your mind about buying it after you discovered it would not fit where you wanted it. It was, after all, your responsibility to make/assure it fit, per #8 as a condition of the sale.
To help you understand how broad a ‘change of mind’ issue can be, you might be interested in this other topic. There is a similarity to your problem, eg ‘it did not fit’.
Restocking fees are common for returns in many businesses regardless of whether a box was opened or not, and that you may feel hard done by, your situation is not uncommon regarding having to pay a restocking fee for returning goods.
Restocking fees can cover potentially lost sales if you had the only stock and they could not deliver to another customer, or in cases where a ‘box’ was opened or protection ripped or removed, it often cannot be resold as new at full price.
I did not suggest I thought it was, however excepting for the form of refund of the 75% that is not well defined, your situation is covered in the contract of sale to which you agreed by your purchase.
Unless another member has a different view my suggestion is to pursue a ‘cash’ refund and write off the 25% as an educational expense. I know that is not what you hoped to hear, but it is how it looks from ‘here’.
However if you were not given a copy of that contract at the time of purchase you may have a position to stand on. Whether you gave them a signed copy at the time could also be relevant.
