NASHVILLE — “Fireproof” had another solid showing in its third weekend, finishing in the top 5 on a per-theater average and passing the $16 million mark for total gross, according to studio estimates. On the strength of its opening in 59 additional cities, “Fireproof” averaged $3,645 per theater to finish No. 5 in that category. For the weekend, “Fireproof” grossed…