So I have a HTML 5 app and I have access to Apple Developer Center (iOS Dev Center to be more exact). The question is can I actually use it without buying (lending) Mac? Mea
No it's not possible.
You can build your phonegap application in the cloud without a Mac (with some limitations depending on the build plan you choose).
As @stu sais, you may be able to make a certificate for Apple Store using Windows.
But, finally, you will need a Mac with Xcode installed to updload your application to the App Store.