Since you are not married, use the Single check box on the Form W-4.
Head of household will be the filing status that will be used on the Form 1040 when filed after the end of the year.
Withholding tables only have Single and Married so you will use Single.
Please ask if you need more help or explanation.
That is correct, use 2
(Technically on the W-4 they are called allowances; but it really is the same thing as exemptions on the 1040. )