How much faster than 99.999..% the speed of light would you need to go to get as fast as the speed of light?
If your answer is 0.00..1% the speed of light, this answer is nonsensical because infinity never ends, and you never ever have the ability to add that 1 at the end. So, the only answer can be 0.00.., and 0.00.. = 0, so 99.99.. has to = 1.
Also, I’d like to understand how if we can say 99.999... is = 100, wouldn’t we also be able to say 99.9999888999... = 99.9999..., and therefore also just 100? And so on?
You've just introduced a novel symbol into the discussion. What is the definition of 99.9999888999...? Before anyone can answer what it equals, you must define it. Recall that if the digits repeat, we already have a definition, so that case is fine. Your case is not à priori well-defined.