I did some maths by myself and the first thing I recognised when trying to solve this numerically was,

that you get an extremly high standard error on b as well as c.

So I looked into the given equation and found that b and c are both defining the base of the exponential function,

so they are to some extent interchangable and only b ̃ is needed:

y=a*(1-(1-0.01/b)^(x/(75*c)) )=a*(1-(1-0.01/b)^(1/c*x/75) )=a*(1-〖(1-0.01/b)^(1/c )〗^(x/75) )=a*(1-(1-1/b ̃ )^(x/75) )

(alternativly you could describe the whole base through b ̃, but this way I found reasonably looking values)

Solving this for crit and alacrity (over 10 points with values up to over 5000 each) resulted in the following values:

Crit:

a=30

b ̃=45

Alacrity:

a=30

b ̃=60

When checking these equations I found minor differences to the actual values,

which can be solved by rounding the base off after some decimals (falls in the range of the standard error).