To enable push email on a windows phone, all you have to do is go into the email settings and change the incoming and outgoing mail servers to m.google.com
However, this will keep working until Google drops the active sync support. However, I have read somewhere on the WP 8.1 features list that better Gmail and Google calendar support was rumored.
Also, forwarding Gmail to an Outlook will save you a lot of trouble. You may call it desperate but it’s the most reliable and future-proof solution you will find.