[stromgo]

I'll answer the energetic question. Splitting water produces oxygen and hydrogen, so with our oxygen we have the choice between burning hydrogen or burning Titan's hydrocarbons. Burning the hydrogen would bring us back to square one, so the question is whether burning hydrocarbons yields more energy than burning hydrogen. It appears to not be the case. Some numbers I found online:

  burning 1 mole of O2 with hydrogen yields 572 kJ
  burning 1 mole of O2 with methane yields 444 kJ
  burning 1 mole of O2 with butane yields 443 kJ
  burning 1 mole of O2 with octane yields 437 kJ
  burning 1 mole of O2 with glucose yields 467 kJ

https://personal.utdallas.edu/~metin/Merit/MyNotes/energySci...

https://www.ausetute.com.au/fuelenergy.html