I’ve calculated that I get about 700% of vitamin C through my diet so I wonder if I should bother supplementing with it for now?
I really don't know. There's debate about how much vitamin C we need. How much is the 700% you are taking? Some people advocate very high doses and others not so much. How's that for an answer!

You can do a search for posts on vitamin C, or you might do a separate post just about vitamin C, trying to find the best dose. Are you working with any sort of practitioner on these issues?
I think you do need to educate yourself about safe detoxing. e.g., chlorella is often recommended for mercury and heavy metals and yet many cannot tolerate it - it can mobilize toxins and get them moving in the body and then they just resettle. It can actually be harmful.
As I said above, I found that glycine especially was very helpful for detoxing. I detoxed for years, I'd detox at the drop of a hat - anything that had "cleansing" properties (e.g., apple cider vinegar) would cause a detox reaction for me. 20 minutes in a far infrared sauna wiped me out for 3 days. And it never got easier, until several months after starting glycine, inositol and glutamine. I rarely get detox symptoms now, unless I have heavy exposure to something. So these 3 things are not herbs, 2 are amino acids and one (inositol) is considered a B vitamin. I don't know if others will benefit as much as I did from them, but if you do give any of them a try, start low and go slow until you see how you react.