A wide and natural class of closed currents -which are differences of positive closed currents -can be constructed by pulling back smooth closed forms using rational maps. These currents are very singular in general, and hence defining intersections between them is challenging. In this paper, we use our previous results to investigate this question in the case where the rational maps in question are pseudo-isomorphisms (i.e. bimeromorphic maps which, along with their inverses, have no exceptional divisors) in dimension 3. Our main result, to be described in a more concrete form later in the paper, is as follows.Theorem. Let X, Y be compact Kähler manifolds of dimension 3, and f : X Y be a pseudo-isomorphism. Let α2, α3 be smooth closed (1, 1) forms on Y , and T1 a difference of two positive closed (1, 1) currents on X. Then, whether the intersection of the currents T1, f * (α2) and f * (α3) satisfies a Bedford-Taylor's type monotone convergence depends only on the cohomology classes of α2, α3.Special attention is given to the case where T1 = f * (α1) where α1 is a smooth closed (1, 1) form on Y . It is then shown that satisfying the above mentioned Bedford-Taylor's type monotone convergence is asymmetric in α1, α2 and α3, but in contrast the resulting signed measure is symmetric in α1, α2 and α3. We relate this Bedford-Taylor's type monotone convergence to the least-negative intersection we defined previously. These results can be extended to the case where α1, α2, α3 are more singular. The use of global approximations (instead of local approximations) of singular currents and dynamics of pseudo-isomorphisms in dimension 3 are essential in proving these results. At the end of the paper we discuss the intersection of currents which are differences of positive closed (1, 1) currents in general.