Yes, use a starter or pitch more vials/packs of yeast.
Bucket or carboy is fine, the beer and the yeast dont really have a preference like we do
Top up til you hit your og, 5.25 gallons is usually what i do.
i would only secondary in a 6 gallon carboy if i purged it with c02 first.
Oak cubes are personal preference, i would primary 4-6 weeks, seconday on the cubes for a month or so, and then bottle age it myself.