Q: What to do in case of delay at the journal end and no response from the editor?

I hope the journal you have submitted to is a reputable one. You should keep sending emails to the AE. You should also send an email to the EiC or any other email address that is there on the journal website. While it is true that editors are sometimes non-responsive, there could be other possible reasons why you have not received a reply. Perhaps the AE has changed or is not receiving your emails. Mark a read receipt for all emails that you send. That way, you'll at least come to know whether the editor has opened your email. 

If even after all your attempts to contact the AE or EiC, you receive no response, you should send a withdrawal request. However, remember that the withdrawal process will be complete only once you receive confirmation of withdrawal from the journal. You cannot submit your paper elsewhere before you receive a confirmation; else, it might be considered duplicate submission.

If you receive no response even to your withdrawal email, you will have to write to the journal saying that you will consider the withdrawal process complete if there is no reply within a specific period of time (set a deadline of a few weeks). You can submit your manuscript to another journal if you receive no response within the stipulated time. However, make sure you write to the editor of the second journal, explaining the situation and providing the email threads about your attempts to contact the journal as supporting evidence to assure them that there was no intention of duplicate submission from your end.