Rob
You can fill those voids with acrylic or epoxy just like the scorpion paperweights. You can use the West system (a brand name) to coat the whole thing which will finish it and "glue" together any cracks or faults. Most boat repair places will have it or hobby stores that have casting materials for those paperweights. Since the epoxy dries by reaction you can fill a lot of the void each time. I have seen stuff that they use to imbed coasters and coins in bar tops -- don't remember the name. Don't use any coating like varnish or oil on the wood until after you have filled the voids.
I think it will look marvelous
ps HF has the chainsaw blade to fit in your 4.5" grinder -- its called a Lancelot
Google table top epoxy and you will find suppliers of the material to fill the voids -- it is not cheap cause those are big holes!
regards