Oh wow, in case of the Interface solution, i somehow had in mind that after calling the “Get Stats” message in the Tower BP, you also have to make an Event inside the Enemy itself to set the Variable Health to the current HP of the Enemy. But the function itself sets the value (After you hook the Health Variable from the enemy to the Outputnode of the function, like you have shown in the picture), without having an extra event.
The cast to node might also be a good solution, thank you for that, too!