Will applying antibacterial ointment and cleaning a suspected bacterial or impetigo infection with soap cause a potential false positive on a bacterial test/swab for it or mrsa?

No. Treatment sounds fine. If improving, keep it up for 5-7 days

The actions you described would not cause a false positive MRSA culture result. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV and Covid vaccines. Wish you good health!