Interesting. Thanks for sharing your thoughts.
My understanding of merit is that those beings (seen and unseen) hearing that you have done good deeds on their behalf will rejoice. This creates a positive mind state that can help increase their chances of a good future rebirth.
Just think it in the 4 values - Metta, Karuna, Mudita, Upekha. Such act also constitutes a way of developing sympathetic joy (mudita) which - along with compassion, metta and equanimity.
How they receive? They receive by being aware. For example; You remember them, You do dhana on their behalf, you help them to do dhana on their behalf, since they are no longer able to dhana in their form as they do not have a human form body. It's akin to you pour water on the soil where it got a seedling of a plant, then it grows. Yet if you pour the water on concrete, not the same thing result also not same, right? Use simple analogy to start finding out and understand it.