Your ideas are pretty far out from reality. What you assume would happen goes even beyond what the German plan in the Septemberprogramm stated. None of which includes your suggested 'occupation of all of Northern France' or 'seizure of the French fleet' (which how are they doing this again? The Fleet would scuttle itself or mutiny and sail to Britain before they let that happen, it would be a point of national pride). They planned to bankrupt France through a massive 10 billion Reichsmarks indemnity, not wantonly stealing everything that wasn't nailed down (which would be impractical).
Since this hypothetical necessarily involves no invasion of Belgium they can't add those plans from the Septemberprogamm either. Not to mention they are going to have to militarily prop up their puppet states in Eastern Europe during this time.
In short your ideas are pretty beyond what even the Germans envisioned, and assume 100% German success in all their post war endeavors. Which is just unlikely, leading your conclusion to be pretty flawed.
However, as an indication of what the British feared might happen, it might be pretty close. This is the country that went into absolute ecstasies of fear over a naval race that the Germans could never even come close to winning, after all.