Firstly, that’s not how reactiveVars are used - you have correctly defined one (var tmpInfo = new ReactiveVar();), but then overwritten it with a normal variable (tmpInfo = res;). The correct way to set a reactiveVar would be tmpInfo.set(res);. Similarly, to retrieve the value - not return tmpInfo;, but return tmpInfo.get();
However, I’m pretty sure you can’t do this anyway. Method calls are not reactive, so I think there’s no way for the form to recover the correct value of tmpInfo before rendering.