Let $\ell_{1,0}(S)=(c_{0,0}(S),\Vert\cdot\Vert_1)$ be a space of functions on a set $S$ with finite support, endowed with $\ell_1$ norm. Could you answer the at least one of the following questions

1) which subspaces in $X$ are complementable?

2) which subspaces in $X$ are $C$-complementable, i.e. there exist projection with norm $\leq C$?

3) which subspaces in $X$ are $C$-complementable for all $C>1$?

4) I think that spaces $\ell_{1,0}(S')$ with $S'\subset S$ will fit. But are there other examples?