Use "few" with countable nouns. You can count people, so you could say "as few as ten persons", as per one of your examples.
When it comes to percentages, fractions, ratios etc, these are not numbers that represent a count of anything, so you would not use 'few' or 'fewer' unless you are directly referencing the countable items, for example "Fewer than 10% of the people in our survey".
Typically, you'd use 'little' with an amount of something - for example "there is very little water in the bath". As with the example above, if your percentage represented something that could be measured this way, it might be ok to use 'little', but I'm struggling to think of an example. For example, if you were using a percentage to measure the amount of water in a reservoir, a reduced volume of water would be best described as a "low" amount.
However, all of your examples involve saying something is "as [little/few/low] as", and this can denote a minimum amount rather than a fixed figure. For example, if you measured footfall on a street every day for a month and said "there were as few as 1000 people a day on the street" that would mean 1000 was the lowest number it ever reached, and possibly an approximation (or rounded) number at that. For that reason, I don't feel your example of "my share in this company is as little as 1%" is correct because "as little as..." implies that it could be higher, and I would imagine your share in a company should be a fixed amount. If your only goal is to say how low it is, you could just say "my share is only 1%".
