Hi Michael,
Your method is really interesting. We at Enrow have just joined Clay (and there's only one credit per valid email). If you'd like to test something, I suggest using Enrow first with the combination (Name + Company Domain) and then with the combination (Name + Company Name + Country Code). You shouldn't need anything else.
To explain it briefly, the first pass works similarly to other methods, but the second one helps counter fake domains found on LinkedIn (or Apollo) or retrieve the correct domain in the case of subsidiaries (I have plenty of examples). This also saves you from paying for SERP data and applying tons of filters on the SERP.
Good luck!