While photoshopping pictures of yourself having sex with women the same age as your wife is an odd choice for sexual arousal, it isn’t part of a profile that typically is associated with pedophilia. Also, you felt your husband had an attraction to a young woman on a TV commercial and assumed she was under 18. Your husband thought he had seen her in a movie, but you dismissed the idea because the commercial was new.
There are several things about these assumptions that jump to conclusions. First, you haven’t asked if he felt an attraction — you assumed it. Secondly, you assumed the actress in the commercial was not 18, and finally that regardless of her age she could not have been in a movie. All of these assumptions are on your part and, while the photoshopping is odd, he is not picturing himself with children.
Pedophilia is termed pedophilic disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5.) To be classified as a pedophile according to the DSM you would need to be at least 16 years old, at least five years older than the child, and the sexual urges and fantasies have either been acted on or caused actual interpersonal difficulty or severe distress because of the intense, recurring urges. The International Classification of Diseases (ICD-11) “… a sustained, focused, and intense pattern of sexual arousal—as manifested by persistent sexual thoughts, fantasies, urges, or behaviours—involving pre-pubertal children. In addition, in order for Pedophilic Disorder to be diagnosed, the individual must have acted on these thoughts, fantasies or urges or be markedly distressed by them. This diagnosis does not apply to sexual behaviours among pre- or post-pubertal children with peers who are close in age.”
I am elaborating on the definitions because typically acting on the thoughts or severe stress surrounding those specific thoughts are part of the diagnostic profile from either the DSM or the ICD-11. For more information please read here.
Your husband, from what you are saying, has not acted on anything like this — and, also from your description, has not even had a fantasy. Liking an actress on TV is what is supposed to happen. Your assumptions are filling in a story that isn’t there.
Talk to your husband about your fantasies about what is going on and have an honest conversation about what you are thinking and feeling with him. If this proves too difficult to do with each other you can find a therapist from the ‘find help’ tab at the top of the page, or from this group here.