It's somewhat true, but to what extent depends on the school. Part-time scores are not incorporated as part of the USNWR rankings, so law schools have a bit more flexibility when it comes to admitting applicants. However, I'm under the impression that they're held to the same range of academic standards as full-time students.
To answer your other question, the maximum amount a graduate student can borrow from a Stafford loan is $8,500 subsidized, $20,500 unsubsidized AND subsidized (this is per year). The lifetime maximum for a graduate student is $138,500.