Finally discovered and fixed what was causing the "infection not progressing" bug. The infection was progressing, the problem was the "/v show" command not showing the real progress.
Renamed configuration node vampiricFlaskConsumeFood to vampiresUseFoodAsBlood since /v offer should have the same source as /v flask.
Fixed flask letting you create flasks when you don't have enough food with
vampiresUseFoodAsBlood = true.