Answer
Salam (Peace) Dear Harry,
Thank you for your question and for contacting Ask About Islam.
Thank you also for showing interest in pursuing the truth about the constant uproarious controversies and unsolicited remarks or rather accusations made against Prophet Muhammad, peace and blessings be upon him.
It’s good that you took this course to verify the claim and seek the truth for you to “decide about Muhammad”, as you put it. I hope the following will help you make that decision.
All that you mention reflect the ideas of those anti-Islamic people, who are known for their constant attacks and insults against Islam and all that relates to it. But it would have been better if such attacks were based on convincing evidence and irrefutable proofs.
Rather, they use slogans to cast aspersions against the followers of this religion forgetting that they are people in glasshouses and should never throw stones.
All that you mentioned, brother, about the Prophet, peace and blessings be upon him, reiterates the same song with the same tune, trying to depict him as a womanizer. The question here is: Was Muhammad (peace be upon him) a womanizer?
If you read the whole story of this noble figure, brother, including his family life, right from his first marriage up to his death, you will find yourself concluding with a clear negative answer to that question.
Actually what makes these people raise such claims about Muhammad is that they fail to get rid of the distortions that have been made in the Bible, which fill it with all forms of abusive words against the Prophets of God.
So brother, it is no wonder that we hear such insults against Prophet Muhammad, peace and blessings be upon him, as being a womanizer and so on. They find it unfathomable why we Muslims hold our Prophet in such great esteem. But why shouldn’t we?
This is what we are taught by our Glorious Book, the Quran, and the Sunnah of our Noble Prophet, peace and blessings be upon him. You can never find in the Quran, a verse where a Prophet of Allah was given a bad description.
The Quran relates their stories to us in a most beautiful way, that no one can even have a shadow of a doubt about their noble characters. Jesus was given high praise in the Quran as well as his mother, Mary (Maryam 19:15-36). Just read in Surat Al-An`am, verses 82-87, how Allah gave a fine description of the chain of 
Prophets, right from Abraham and down to the rest of the Prophets.
So it should be no wonder to see Muslims holding all Prophets in high esteem; the thing those people find it difficult to adopt.
In responding to all what you mentioned about Prophet Muhammad’s dealing with his wives and his being depicted as a person who wallows in lust, I find it relevant to cite for you the following statement made by one of the prominent Azharite scholars, Sheikh `Abdul Mageed Subh:
“Prophet Muhammad, peace and blessings be upon him, instead of taking concubines, entered into lawful marriages with those women known as his wives, and his marriage to all of them was based on reasons and wisdom. Mariam the Copt (mentioned in your question) is a case in point. She was given to him as a present, but rather than taking her as a concubine, the Prophet, peace and blessings be upon him, married her; thus elevating her status by marriage, and she bore him Ibrahim.
The Prophet’s marriages refuted the idea of asceticism, which Islam rejects. Those who claim to practice it, usually fail to rise to its standard. For instance, in Europe during the Industrial Revolution, churches were razed to the ground to make place for industrial cities.
The surprise was the discovery of bones of children, who were product of illicit affairs practiced by the monks. They found no way to cover their crimes other than killing those children and burying their remains!”
You see, brother, that those citations you referred to in your message are totally baseless. For, with all the Biblical records of something like x-rated pornography attributed to some Prophets, who really deserves to be called womanizer?
Can you tell me, is a man who runs the affairs of his house, enjoying his conjugal rights his wives, to be called womanizer, or a man having 300 concubines (as in the biblical story of Solomon)?
Tell me brother, is a man who enjoys a lawful intimacy with his wives to be deemed as wallowing in lust or a man (as in Esther 2:2-4) for whom young bosomed virgins were searched for to have fun with or (as in 1 King 1:1-4) a young beautiful lady to lie beside him and take care of him? 
So brother, before making such unwarranted claims against Prophet Muhammad, peace and blessings be upon him, it would have been better if an advanced search and checks were made of previous scriptures to see the many corrupt remarks that have been made against the Prophets of God.
We Muslims, of course, don’t believe in such remarks as I have said, but I just want you to know that all this is an attempt to fill people’s mind with distortions about all the Prophets, not only Muhammad. It’s an attempt to shake people’s belief in all that is divine:
{They desire to put out the light of Allah with their mouths but Allah will perfect His light, though the unbelievers may be averse.} (As-Saff 61:8)
Once again, thanks for your message.
Salam and please stay in touch.
(Last Published: June 2016)