Commutators and abelianisations of congruence subgroups in function fields

Question

Let $A = F_q[T]$ be the ring of polynomials in one variable with coefficients in a finite field, and let $r>1$ be an integer. I'm currently looking for the abelianisation of the congruence subgroup $Γ(N)$ of the special linear group $SL(r,A)$, i.e. the kernel of the 'modulo $N$' map $SL(r,A) \to SL(r,A/N)$, where $N \in A$ is a nonconstant polynomial; more particularly, I'm looking for the torsion-free part of the abelianisation, but I wouldn't complain about knowing the abelianisation itself if that's possible.

So, here are my questions, in reverse order of importance:

1. What are the commutator subgroups of $SL(r,A)$ and $Γ(N)$?
2. What are the abelianisations of these groups?
3. What are the torsion-free abelianisations of these groups?

I wasn't sure whether this should be posted on math.overflow instead; please move it if it should be there instead.