Kufr

Q: I would like to bring a matter under consideration regarding my husband, as he said that "he will challenge Allah". 

It all happened when I told him that I want to take separation from him and I mentioned that Allah has given me this right, to which he said no I can't and first he said I can bring any Ulamas I want he will send them all flying, they cannot interfere, I will challenge them all, to which I said okay no problem but Allah has given me this right. It's almost 10 years you can't look after me so I will go away myself and then he said "I will challenge Allah ". Listening to this I told him are you gone nuts what are you talking, you can't talk like this. He stood firm on his statement and after that I kept myself quiet, before he says something more bad. 

Just to mention, he was in his full senses, wasn't angry when the topic started. I keep Ulamas away as he has no respect, but please I want to know what to be done with this statement. 

Also his ibadaat is personal, I don't want to bring that in the picture, but want to mention he used to read fajar at the time of sunrise, which always caused a spark between us. He never use to listen. Now he no more reads, even on big nights and on Shabe Barah he told my son Asar time that books are already closed we don't need to make ibadat. I was completely shocked and explained to my son that we have to make ibadah till fajar. So I'm not sure what is his say in religious matters. 

Please I want to know what is the way forward with it.

Q: If a person, due to slip of tongue, said something of kufr while not intending it, is he kafir? 

For example, a person wanting to say that "one who rejects God is not a Muslim" but he accidentally says "one who rejects God is not a kafir" but then he realises and corrects it. Does he have to renew his iman and nikah?

Q: Someone believes there's no worldly harm of listening to music as it has benefits scientifically, however they believe music is still a sin, and that this argument doesn't justify it nor renders the ruling mistaken. And that music is sin. Are they kaafir?

Q: Is boasting about ones sins an act of kufr, if one's belief is that the sin is haraam and wrong.? Like in today's time many people boast about zina, alcohol. etc.  

Q: Is it kufr to make realistic art of living beings? I know it's haram and major sin but is it kufr?

Q: What is the status of a person who insults Hazrat Abu Bakr and Umar (radhiyallahu anhuma) or any other Sahaabi? May Allah Ta'ala protect us.

Q: 

1. If someone rejects a tenet of Islam due to lack of knowledge, are they kaafir? Example: Believing not doing waajib acts doesn't entail sin, only fardhs entail sin. 

2. When it becomes known to them that the act is a tenet of Islam, they accept it. Do they have to reclaim shahaadah?

Q: A person called someone a kaafir but this person had no idea that the person he’s talking about is actually a Muslim due to the fact that the person he spoke about has a kaafir name and made no clear indication that he was a Muslim. 

In this case, does it make the person that was speaking about the other person a kaafir?

Q: What will happen if a person commits kufr but later forgets about it? 

Secondly, if you get bad thoughts about Allah Ta'ala and you feel the sensestion of happiness about it but you know thats bad, is this kufr too?

Q: If a Muslim commits an act of kufr like mocking Allah Ta'ala, will saying the shahada be enough for him to become a Muslim again or is repentance mandatory. If he just says the shahada, will he become a Muslim even if he doesn't repent?