I think you are asking a bit wrong if what you really want to know is if a province with explosions on risk gtting both explosions on shipments they sent and recieved. That is indeed the case, but since it is a % chance it will not happen on every shipment, the wiki says it is 50% chance/risk depending on point of view.

The reciever is I believe taxed by the original shipments value just like when aiding acres, the seder get the original shipments value in supplus. The only senario where it might be diffrent is if the sender has explosions and the original shipment thus gets reduced before reaching the reciever, there the reciever might not get the full value detracted from their trade ballance, but I believe this senario probably is not true.

If your last question should be read as does a shipment from a province with explosions risk getting exploded twice if the reciever also has explosions the answer is no, but with a 50% risk both ways the effective risk of the shipment getting exploded rises to 75%.

If there is tax for the recieving province this is detracted after the reduction by the explosion.

Most people only gets to experience explosions occasionally as it is mostly deployed against key provinces to prevent aid to chain targets or from t/m's or other unbreakables in war, in which case it is almost always removed before sending aid, or occasionally to try and starve a province for a few tics which is rarely succesfull unless that province has gone offline in which case they could not ask for aid before they got on again anyway, and if they got on in time they could simply steal.
You can also encounter explosions after randomming a t/m or someone else unable to retal that will sometimes cast every spell they have avalible at your province to show their displeasure.