That ensemble sounds fine to me. Sweaters have long been worn with the kilt. The choice now becomes, do you tuck the sweater in or leave it out. This question is usually solved by the bulk of the sweater. Large bulky cable stitched sweaters seem to look better out, and smoother, less bulky sweaters look better tucked in.

As to wearing a tie or not, that depends on the neckline of the sweater. If the tiecan be seen, wear one. If it is completely hidden - why bother?