This is emphasised by that a few may mean 2 or even 1, whereas several should not.

Just "few" could mean 1 or 2, "a few" is at least 3 in my book.

As an Australian I agree with you. I would definitely expect several to be more than a few. Most of the time "a few" would mean 3 or 4, to me. "Several" is anywhere from 4 to ~7.

That's close to my take from the SF Bay Area too. A few days over a weekend would strongly tend towards adding either Friday or Monday but not both.

I do consider that "a couple" is imprecise and varies by context. Asking for a couple cloves of garlic while cooking could mean 2-4, especially if they are small. Asking for a couple bulbs of garlic on a shopping list could only mean 2!

For items, I think I'm also more like to shift into "half a dozen" or "dozen" than expect common ground on what "several" communicates. For days, I think I'd shift to "a week" or "N weeks" as soon as it spans a Monday-Friday work week, even if the start/end weeks are partial.

I always consider several to be in the region of about seven due to the first syllable. Few would be in the 3-5 range, several 5-10, many 10-15 and lots being more than that, but it’s also context based too. If there were 7 apples in a bowl I might say several. If there were 7 nuts it would be “a few”.