Almost positive the EPA made diazinon a restricted use product, so can't purchase without a license now.
When I get in over my head with too much to do and not enough time or just plane tuckered out I'll settle to debark 1 stave a day or every other day, so long as I keep at it even at a slow pace. Provided the ends are sealed and I can get them out of the weather till they get done. Like Superdave said, get the ends sealed and you should be good.
I do think removing the bark and sapwood is best. 1 time I had a load of hickory come in show up at the firewood processor that was cut that day. Spent days splitting and with the growing season just about to start knew I would not have time/energy to spend removing the bark. I researched boron products(like you stated above). Timbor and Boracare are made for wood boring pests. Forrestry forms have a some good information about those products, just google to find. On a side note Timbor seems to be the same active ingredent as borax and solubor(an agricultural micronutrient). Coverage is key, just like a diazinon. You can find the SDS info online but the boron products are as safe as anything and provided the staves stay dry it will remain active. Worked very well for me. Of course you always want to follow the label
Good luck with the rest of your project, looks like some killer staves.
Mike