Have you ever tried a 'Buster Cube'? I think they still make them. (the one I have is over 10 years old)
Its a plastic cube, shaped like a dice. Its a food puzzle. You put kibble in it. You adjust the opening so its easy to get out at first... so they get the hang of it... then gradually make it harder.
They roll it around the floor and it can take 10 minutes or more to get the food all out. Its also entertaining. For them and me.
There are similar products that are round. They work okay for some dogs but just having to roll it makes it too easy for some dogs. Not enough of a challenge.
You can also put meals inside a kong toy and then adding water so the food expands and doesnt fall out easily. If thats not hard enough, freeze it.
You might try feeding his meals only with these type of toys for a while (how long?
) to try to break his typical feeding pattern. Then just always incorporate requiring calm behavior, before you give it to him. When he is good about staying calm for his food toy, try changing back to the bowl.
I know several people who ALWAYS feed that way because their dogs really like it... prefer it to the bowl, even.
My dogs dont really eat that way (well, Libby just a little) but I give them the cube or Kongs occasionally, partially for my entertainment, partly for their enrichment.
If you feed raw... try freezing it. It slows them down and it shouldnt splatter.