Mama Solter, I'm very sorry your dog had a problem and i'm so glad he is doing better now.
i still stand behind micro chipping as i think the risks are very low compared to the benefits. none of the articles given talk about what % of total microchipped animals have problems, i would guess it is left out because the actual percentage is amazingly low. and as the second link mention that having one gave a 30% better chance of getting your dog back from a shelter, that is nothing to shake a stick at.
many things we do, we do understanding that there is some small risk and we choose to do it because the benefits are something we want. while i would never want to downplay the horrible stress you and your dog went thru (i had a 10year old extremely beloved cat nearly poisoned to death, so i very much understand the stress, i still 10 years later shudder and tear up thinking of those few weeks) i would mention that your dog is more like to get sick from dozens of other things you freely do with him on a regular basis. I'm sure more dogs end up super sick or worse from things they step on in dog park or beaches than get sick from microchipping.
and while this is totally anecdotal, i would like to say that i had 2 cats chipped in the early days of chipping, both when they were just a few months old. one was totally healthy till 8 years old and then was stricken with numerous cancer things involving various body parts, but nothing of any issue with the implant at all, heck it might have been the only inch of her that didnt have a problem when we laid her to rest. her cancer was clearly something she had a genetic propensity for based on th way it spread in her body, i do not believe it had a particular external cause.
my other cat lived nearly 17 years with his chip and finally passed away from slow growing cancer of the GI that matasified in to the lungs, this was a very normal and totally age relater cancer in cats and in my case an other wise amazingly health cat that shared nearly half my life.
so i had two cats die of cancer, but the fact is a huge number of cats die of cancer, a huge number. so its always good to remember that correlation does not necessarily mean causality