Yes, you have already clinched the division even if you lose your last match. One correction though, due to the seeding format of the NFL, you are the #3 seed because you won your division -even if TheRinger has a better record. It's something I'm thinking of addressing next season and having seeding based on record but still have the 4 division winners get a playoff berth.
For @trinity747 (unclepappi777), this last match is important because if he loses there will be three teams at 9-7 - I'd have to figure out who advances in that scenario but I'll do that after the match if necessary. Also, @PeaceChaser still has a couple games going so that will have implications as well.