Partition of a set of integers into subsets with prescribed sums
For any fixed $k$, isn't it in P, by dynamic programming?

For each $i\in\{0,\ldots,n\}$ and $t_1, t_2, ..., t_k$ such that each $t_i \in \{0,\ldots,m_i\}$, define $S(i, t_1, t_2, \ldots, t_k)$ to be true iff $(t_1, t_2, .., t_k)$ is $i$-realizable.  Then there are $O(n^{2k+1})$ such subproblems (assuming WLOG that $\max_i m_i\le n^2$), and you have a recurrence like

$ S(i, t_1, t_2, \ldots, t_k)$ 

$~ = S(i-1, t_1 - i, t_2, \ldots, t_k) $

$~\vee~ S(i-1, t_1, t_2 - i, t_3, \ldots, t_k)$

$~\vee~ \cdots$

$~\vee~ S(i-1, t_1, t_2 , t_3, \ldots, t_{k-1}, t_k- i)?$