See here's the thing, no matter which proof you bring towards these kuffar, they will not believe because their mindset is set in that way of thinking, and it is Allah (swt) who tests, guides and leaves astray those who do not wish to be guided.
All these are typical arguments of people who do not have the knowledge nor context of the qur'an, who pretend they are knowledgable and appear so, who pretend they are even linguistic and understanding arabic, etc...
I've witnessed myself ARAB muslims and so called 'ex-muslims' trying to say there is no hijab of any sort in the qur'an yet it is there. We've had one such person here (a troll).
As far as the clay, earth, water arguments. Remember, the qur'an was revealed to a people who did not have an understanding of atoms, molecular science, physics, chemistry, etc... it was explained to them in a manner they would understand, however today when we read some such things it makes sense to us.
#1 For example we know today there cannot be life without water, we know the universe in it's creation was made up of water and our bodies are made up majority of water.
#2 The whole earth and clay arguments, is it that far fetched to accept? Not at all. What is our body made up of? The contents of the soil is what? Earth elements. Our body is EXACTLY that, made up of earth's elementary molecules. No really. Zinc, iron, oxygen, hydrogen, you name it. That's it.
The setting on horizon thing, I forget the elaborate explanation on that, but still, the qur'an has parts where things are explained as moving bodies in orbit if i recall linguistically specific worrds being used.. and if not that specific verse it's an expression. Do we not say sun has set? What's wrong with that either? A statement does not always have to be a literal statement. Although I would allow someone more knowledgable to explain this one as also I forgot but it's nothing what THEY these non-muslims and 'ex-muslims' claim. They just copy paste the same arguments that many christian missionaries do too. That's all they do, day and night and fool people without knoweldge.
I have learned from observing amongst muslims that alot of muslims derive their iman from BAD and false things, meaning they look for some stupid things like 'miracles' in a cloud seeing "Allah" or name of Allah in tomato.. RATHER THAN equiping themselves with KNOWLEDGE.
KNOWLEDGE of Allah, of the prophet, of Islam, of the sahaba etc.. should INCREASE our iman. Lack of knowledge results in people manipulating you because they play on you lack of knowledge, that is exactly what these people do. to the extent that they might even convince you because they sound like they know what they are talking about, when in fact you just lack the knowledge.
Many muslim sects and groups even they 'increase' their follower's iman with false stories or fabricated weak hadith (tabliqhi jamat) yet when they find out these are not true, their iman will decrease.
The other problem is some muslims try to find 'scientific miracles' in the quran in everything.. so theyll make up stuff. Like take a verse that is elusive and apply something allegedly 'scientific' this is so wrong. This is another problem. Yet what was the qur'an revealed for? FOR GUIDANCE, it's not a book of science, it is a book of SIGNS as Dr. Zakir Naik often says in his speeches.
Iman is increased with knowledge of truth and seeking knowledge is mandatory upon every muslim.
"so called ex-muslims" so called.. hmm