It's a 15 place penalty for changing your power unit and a 5 place penalty for ignoring red flags (3 points on your licence is meaningless).
F1 Priority: Cost of Power Units > Major Safety Infraction. Jules Bianchi would disagree.
This sport needs an enema.
Maybe Vettel would have gotten more serious penalty if his action would have actually caused danger? Do they wave only red flag in these situations? Maybe have red + yellow flags waved simultaneously where crash (or what ever caused red flag) occurred? It would also mean the same as local double yellow.
Ignoring red flag: 5-15 place penalty depending situation
Ignoring yellow flag: 5-15 place penalty
Ignoring red + yellow: 10 place - race ban
Ignoring double yellows: 10 place penalty - race ban
Depends on how deliberate it was; how much time there was to react etc. For example in Vettel's case it would have been close to that 15 place penalty.