1. 楼主的理解错误。
如果单是have的反意疑问句,楼主就说对了。
单是如果是have to的话,就不能这样变反意疑问句了。
2. have to的反意疑问句,必须用don't sb/sth(必须是人称代词主格)?
因为此时的have,既不是行为动词,也不是助动词,have to是一个类似于情态动词的短语。
如:You have to go now, don't you?
3. 当然,如果是:
1)has to,则用doesn't sb/sth?
2) had to,则用didn't sb/sth?
3) will/shall have to,则用won't/shan't sb/sth.
参考资料:原创回答团(第159号会员)