Identifying chords with multiple extensions

I understand that this may be basic. I have a chorus progression (C major) I am working on, and it originally started as basically the following:

I-VII-V-vi-V

I wanted to experiment a little by added notes outside of the triad. Then I thought I would just hold the G and C notes from the I chord throughout the rest of the progression. I like the effect, but I need to know more specifically what exactly I did and how dramatically I altered the chords. Here's how it looks now:

Can you help me identify the new chords? This leads to a broader question I have been curious about. When you add a seventh, say, to a V chord, you get a V7. When you add a sixth to a V chord, you get a V6. But what about when you add a sixth and a seventh? Or a sixth, a seventh, and a fourth? Is it a game of "majority rules" regarding how to name the chord? Does the root note carry more importance than other notes?

I would be very appreciative if you could help me get to the bottom of this! Thanks!

-286642

One such non-chord tone is the pedal (or pedal point), where a pitch just holds through without changing. And this is exactly what you have here: After your I chord in m. 1, the C G both stay as pedal points as you move into VII.
But you're right, when you add a sixth and a seventh, you start to create a bit of a cluster chord; sometimes it's best to go with Occam's razor and find the more basic solution. Your last measure, for instance, might best be understood as a Gsus4 (there's actually not an add6, because there's no E). Similarly, your V? might best be viewed as a C/G chord with a D non-chord tone; but others would be comfortable calling that a Gsus4add6.