Link webform to a specific node
I think you should be able to do this fairly easily, without even involving views or contexts!

Here's how you can do it:


Just like you said, you can create a new Entity Reference field that will point to the relevant webform.  I'd make this field an Autocomplete (Tags style) field:

When you're setting up your field, make sure to select that it should only pull from your Webform content type:

When you've created the new field, make sure you hit the 'Manage Display' settings on the content type that includes this webform reference.  Here's where the real magic is going to happen: you can have this new referenced entity (which is your webform) be displayed not as a link, but as a rendered entity.  Which means you can just automatically display the webform under or above your node, or whereever you choose to output it.  In my case, I made it the very last field (so it displays under my node), and here are the exact settings:



Now test:
If you go to create a new content type, you should be able to just start typing in the title of the webform you want to attach (such as "Contact Us"), and all the matching webforms will pop up - just choose the right one, save, and it should appear under your node.



Voila! 

Let us know if it works for you.