New H1b does not care your old paycheck tub. But, if it is not enough salary which the old company have paid you, the old company will have a problem for applying for H1b for others again because there may be a fraud case.
2) 新公司職位似乎技術性不強, 如INS不給transfer, 我能不能回現公司工作? (現老板應不知這事, 我可辦加快的transfer).
you can go back, but you must extend your H1b if it will be expired.