Sweetheart, as I am sure you know, sex on October 12 and would produce a baby July 5, not in August. The first guy's sperm was long dead in your body by the time you ovulated and got pregnant.
You ask if "traits" are more "authentic" than dates; I assume you are asking if they somehow disprove how long pregnancy lasts. No, they don't.
Sme things to remember: First of all, you are the one looking for these traits, and you have looked at probably a hundred traits in your child and are obsessing over only the few that your guilty secret is leading you to obsess over, and overlooking all the rest because you are worried about a (very unlikely) fear. More important, traits in children come not only from you and your partner, they come down from your mother and father, your partner's mother and father, and all their mothers and fathers all the way up the line. I knew a guy with quite dark skin whose eyes were grey. Nobody in his immediate family up to his grandparents had grey eyes. When he did an "Ancestry.com" test he found a portrait someone had posted of his great-great grandfather, and there were those grey eyes. He was surprised and quite delighted. Some traits are recessive in the family line and pop up only when the genetics allow.
Your child might someday do an Ancestry.com style of test just because they are interesting. The only way there would be a surprise in it is if your memory of the date of the sex being no later than October 12 is faulty, which it doesn't sound like it is. I also assume that at the time you weren't worried, because you had a period between the men? Please keep that in mind too.
It is possible to get a DNA test from Ravgen called a "discreet" test, in which you send in your partner's toothbrush or a swab run along the edge of his drinking glass. Your dates are so obvious that it would be a waste of effort to go this far. But if you seriously cannot stop worrying about things like chin dimples and clefts, AND if you think a test proving your partner is the dad will overcome your worries, it is possible to test without your partner knowing. I don't recommend testing because your dates don't suggest a problem, and often women whose guilty secrets are running the show are not soothed by a DNA test either, and then they have wasted all that money. But you know yourself best.