Aamir "bol sakte hain" is also correct, its like giving respect to him, just like "vous" and "tu" in french
Yes, you are right. When using the respectful form, you often also add the suffix 'ji' to the name - "Aamirji bol sakte hain' but it is not wrong even without the 'ji'.
Does the sentence 'Aamir ko bol sakta hai' mean anything?
It means amir can speak