Critical Reasoning (Subjective and objective):

How many issues/subjects are here?

Two.

What are these?

1.) Guidelines for social friendship or association

and

2.) Guidelines about the food (Rizk) or social invitation

What type of statement is it?

It is a prohibition.

What does a prohibition mean?

It is regarded as Haram.

Can you then befriend a kafir?

No! It would be haram

How do you know a person is Allah-fearing or not?

Very easy. You have known him for some time that he has been involved in Haram things, and you remind him about the haram with wisdom and still you find him does not change or comes out from the Haram by using different logic which clearly shows that he does not have fear of Allah, he knows only that “Allah will forgive” but he continues in Haram.

Can you then invite such a person into your home who is not a Muslim or a so-called ‘Muslim’ (by birth) who does not follow or obey Allah or engage in Haram, shirk or in Bida’a? (as logically, a Muslim who fears Allah can’t do those things)

No! It would be clear Haram.

Then, is it Haram to invite such people to your functions and ceremonies?

Yes, clearly. Because who do you invite to those functions? Your friends and associates, and it is Haram to be friends with those people in the first place; therefore, inviting them to eat your food makes it a double act of Haram!

Is it possible that Allah gives you barakah in your Rizk when you use your RIZK in a Haram way?

I don’t think so!

Does it mean that you don’t give charity to such people? 

No, that’s a different issue. That does not have a relation with that.

Does it also mean that you don’t give the proper rights to your neighbours who is not Muslims?

No, that’s again a different issue. You just can’t befriend such neighbours, but then be very careful about their rights as neighbours. And Allah knows best.

Do you have any sharia’ guideline about this?

Yes, here it is. Read carefully when you have time and intention, so that you really do not involve yourself in Haram.

And Allah knows best.
May Allah make us firm in following HIS Deen strictly.
Ameen.