Is it permissible to stipulate taking the earnest money if the buyer backs out, and paying double the earnest money if the seller backs out of selling a store? And if it is not permissible, what is the ruling in case of disagreement?

Withdrawing from a sale before its completion is a withdrawal from a promise that does not entail a financial right unless the promised party incurs damage, in which case a sum equal to the actual damage is estimated for them. However, if the sale is complete and part of the price has been paid as a deposit, the seller is not allowed to withdraw and must deliver the sold item, and the buyer must pay the remaining price. The buyer may release the seller [from the contract] in exchange for a sum paid to the seller along with the return of the deposit.