How do I render a custom form on a view page?
It's only possible to display one "page" on a url, so you can't both display a view and a form or any other "page" for that matter.

You have a few options:


Insert the form into the view (can be done with a global views handler)
Insert the form on the view page by exposing it as a block.
Insert the view on the form page by exposing it as a block.


Probably the easiest solution for you is to convert the view page to a view block and insert it on the form page. Views already has support for this, so you only need a few clicks in the interface to achieve this.