1. no need. Change name at N-400 stage, free and fast.
2. 5 years since LPR (2 more years to wait) or 3 years since an LPR's marriage to a US cirizen (3 more years to wait), so your new marriage will not help you shorten the wait.
2. 5 years since LPR (2 more years to wait) or 3 years since an LPR's marriage to a US cirizen (3 more years to wait), so your new marriage will not help you shorten the wait.