Hello Andrew, that is a beautiful practice
bhavanirodha wrote:1. Has anyone tried this before, or read about such a practice?
I have not, but it sounds nice, I will incorporate it and tell you how it goes.
bhavanirodha wrote:2. Is there anything risky, dangerous, arrogant or condascending implied by such an extension of metta?
Not at all, the point of metta meditation is to extend the love to all beings, in my opinion, it is only logical to reach the bodhisattvas at some point.
I recently heard a talk that explained how to generate good karma, and basically, when you do good deeds, bow, or have good feelings, etc... if you dedicate them to higher beings such as the Buddha, the karma you create is much better. Not to encourage anyone in dedicating the practice just to get better karma, but yes, it is definitely good, just remember humility and you will be fine.
bhavanirodha wrote:3. If you are of the opinion that such practices of metta-bhavana can affect other beings at great distances or outside direct interactions (quantum-cetasika-entanglement?), do you think that such elevated beings are beyond such small help as my little 'metta-waves' or do they still benefit?
Yes, they can affect, all thoughts and actions have an effect and this is not an exception.
bhavanirodha wrote:4. What is the Bodhisatta's current name?
I honestly don't know, but this is a list that might help: https://en.wikipedia.org/wiki/List_of_bodhisattvas