The young woman Kane sets out to save is named Meredith. This was a Welsh surname, but when used as a given name (often as a patronymic) it was given to males. It didn't become a female given name until nearly 300 years after the time period of this film, and then mostly in the US.
In the film, ships are shown flying the British Union Jack flag with the caption "North Africa: 1600". However, the first variant of the Union Jack (the one shown) wasn't used until 1606 - with the current version of the flag not seen until 1801.
The ship shown crossing in front of the burning city in the beginning of the film belongs to a type who appeared much later. The plain bow design, the lack of square sprit-sail, the jibs and the aft marconi sail are features typical of a nineteen century or later ship.
When Solomon Kane meets up with the Crowthorn family, the father shows Kane a locket with photos of his wife and daughter. Photography had NOT been invented in this time frame. And, it's not likely those pictures were portraits, as they looked exactly like the characters.
In the scene where Solomon meet the thieves from the woods again, there is an statue of an angel kneeling with the sword on its left shoulder in the background. The next scene when Solomon is leaning against that statue, the sword is on the right shoulder.
The pistol that Solomon Kane used is a Wheellock not a flintlock. Therefore the cock/hammer and the frizzen wouldn't move as the flint was sparked by a wheel that turned to provide the spark to ignite the powder.
At the beginning of the film, Kane is shown having retired to a monastery. While a large number of English monasteries, priories, convents and friaries were disbanded and destroyed under the orders of Henry VIII during the mid-16th century, this dissolution was not total and some survived.