See, this is EXACTLY why you need to stop asking so many questions, and study the life of the Prophet (May Allah send peace and blessings upon him). I can recommend a seerah for you, by Mufti Menk.
Abu Lahab was told he will enter the fire because of his mockery and rejection to the Prophet. DON'T TAKE EVERYTHING I SAY AS AUTHENTIC, but from the top of my head I will answer why.
Basically, once the Prophet gathered the people of Mecca (Not all I think) to a mountain, and he said,
"If I were to tell you guys there is an army on the other side of this mountain, will you believe me?"
The people replied, "Yes!, we believe you are the truthful one, you would never lie!" (They said this because the Prophet (May Allah send peace and blessings upon him) was known as that even before prophethood.
So then the Prophet said "Then accept my message" (I'm paraphrasing)
So they I think most of them started to mock, if not all, I cannot remember, maybe some of them accepted, I can't remember.
Then Abu Lahab mocked too, so the Surah was revealed, and people around Makkah were reciting it.
The shocking thing about the surah is, that Abu Lahab could have easily accepted Islam and proven the surah wrong, thus proving the message wrong, but he did not, he could've even faked to accept it to prove the message wrong, but he didn't!
My advice is STOP ARGUING with ignorant people who are here to mock Islam, GO AND STUDY THE LIFE OF THE PROPHET FIRST (May Allah send peace and blessings upon him). I used to be the way you were, I would just sit and argue with ignorant non muslims and then I would get silly doubts, instead of focusing on studying Islam etc.
STOP BEING A SKEPTIC. It's for your own good.