As easy as ABC, “The Jacksons: An American Dream” high-stepped to a big finish Wednesday, ranking as the highest-rated miniseries in more than three years and lifting ABC to what should be an insurmountable lead in the November sweeps.Part 2 of the five-hour miniseries recorded a 23.9 rating, 36 share, bringing the two-day average to a 22.2/33, the best for a multiparter since NBC’s “I Know My First Name Is Steven” in May 1989. The second half attracted more than 38 million viewers and also showed “The Jacksons” to be a network programmer’s dream in terms of audience breakdown, including a 41 share of adults 18-49, 50 share among women 18-34 and 62 share with teenagers. A special 8 p.m. airing of “Home Improvement” (17.4/27) also easily won its time period, helping ABC score its best Wednesday rating since it aired the Academy Awards there in March 1989. ‘Seinfeld’ looks good Despite the stiff competition, “Seinfeld” (13.0/19) had its best household rating of the season. Through three-quarters of the 28-day Nielsen sweeps, ABC is now averaging a 13.6/22, well ahead of both CBS (12.6/20) and NBC (11.8/19). Both ABC and Fox Broadcasting Co. (8.1/13) are up compared to their year-ago performance, while CBS is down a modest 1% and NBC is off by 10%. If ABC’s lead holds up, the web will claim its first November sweeps crown since 1978, its first major sweeps win since February 1988 and only its fourth victory out of the last 30 May, February or November surveys. CBS would have to beat ABC by more than three rating points over the next seven days to overcome the current deficit.