I don't think it matters how often you do !g, you're still going through ddg, which suggests ddg has a better relationship with you than google.

In facilitating your use of google for your specific searches, which you apparently can determine the likelihood of beforehand, ddg gets more of your searches for everything else. This is definitely a win for you and ddg, perhaps even for google if it increases your dependence on queries in general.

Also, I don't think ddg is trying to replace google. From your numbers, ddg is getting ~ 30% of your queries without having to implement deep search.

ddg doesn't log ip addresses/track you, so they could only probabilistically identify cases where people think ddg would do better but then fall back to google, but it will likely get harder and more computationally intense as they grow.