“Director-choreographer Twyla Tharp’s surreal spectacle set to Bob Dylan songs is now somewhere between Draft 2 and the final Draft 3 that will open on Broadway this fall. Those terms come from Tharp herself, who calls a private workshop performance of the fledgling show last year in New York “Draft 1” and the Globe show of two months ago “Draft 2.” In residence here since early December, the workaholic Tharp has attended most of the 65 performances since previews began.”