Wirklich mit me?

Der Angesprochene soll nicht mir die zehn Minuten ersparen, sondern sie für mich aufwenden ... (for a chat with me).

Zu #3:

Ich würde formulieren:

Do you have half an hour to chat with me?

”  

#7 is chiefly BE. I could guess it from the context, I suppose, but if you want to be sure that AE speakers would understand it as well, I'd use one of the other suggestions here.

Wirklich mit me?

Der Angesprochene soll nicht mir die zehn Minuten ersparen, sondern sie für mich aufwenden ... (for a chat with me).

As others have pointed out, "spare me some time" is correct. In this case, "spare" is used in the sense of "give":

From Cambridge:

spare verb (GIVE)

to give time or money to someone:

I have to go soon, but I can spare a few minutes.

[ + two objects ] Can you spare me some change?

I'd say that it also works without the "me," though.

I'm not so keen on the chatting in #0; I'd say

Have you got/do you have...

...half an hour to chat

...half an hour for a chat

(Bubb, I don't have a problem with the 'formality' of 'half an hour'; I think I'd tend towards 'half an hour' in everyday speech over 'thirty minutes' - it trips off the tongue quicker, because the words blend into one another better, and if you slur 'hour' it's one syllable shorter! 😊)

#1-#5: Mit "spare" würde ich es eher so formulieren: "Have you got half an hour to spare (for a chat)"?