Co-signers cannot be used for a spousal sponsorship.
Yes...he's the principal (and only) applicant for PR.
You are applying to be his sponsor.
Just want to make sure that you understand:
Everything gets sent together in one large parcel (your application to sponsor [and related/required documents], his application for PR [and related/required documents], your evidence of a genuine relationship [usually, a lot of material].
You pay the fees ($1040 total, of which $550 must be paid before sending the application). It's suggested to pay the full amount up front, if possible.
If he's submitting an Inland application, and still has legal status, he can include an Open Work Permit application as well (fee is $155+$100).