As to the longer quotation, I'm not sure about the last clause, but "'Twould 'a' ben a dum sight better, all around" means 'It would have been a damned sight [i.e. "very much"] better, taking everything into consideration [or "for everyone concerned"]..." . In the last clause, either 'to start someone along' is a dialect phrasal verb that I haven't met, or "along last summer" is to be read as a whole - in which case the clause means '... if they had started him [at what, I don't know] round about the beginning of last summer.'
Best I can do, I'm afraid.
Student or Learner