The probable answer to first is that tamim ad dari found dajjal when he was still tied up. Secondly, being in different dimenesion does not mean he would not at all come to our dimension. As for third question: Dajjal being in the east might be his direction of emergence or direction of presence at that particular time and so forth. Being in east does not mean dajjal would not travel. Note: Im being a advocate because I do not see your questions are crucial points to falsify the ttheory. And not because i do not have my own personal reservations about it.