An algorithm is not going to be able to dial in your fit to within 10 mm. There is no point to obsessing over minute differences in the output from these sites. Just use them to get you in the ballpark, then pay attention to your body.
Yes, for example, if your hands are getting numb, it's often because you have too much weight on them. Improving core strength and adjusting stem extension can be a part of fixing this, but you should also experiment with moving the saddle back, i.e. increasing the saddle setback. You can do this by sliding the saddle back on the seatpost 5 mm at a time without modifying the tilt. You may find as the saddle goes back that the saddle needs to be lowered a little. You may find that 1 mm adjustments are not too small, for both the saddle height and the saddle setback.
If you have a frame that is within that 1.5 cm range that is essentially golden, for frame size. You need now to see if you can dial in your contact points (saddle support points, pedals, handlebars) with that frame. If you run into places where the frame or other parts limit you (I often find I want more saddle setback that I can get with a zero-setback seatpost), then you need to change parts or even the frame for fit reasons. I don't believe the calculators can set up in this much detail for the wide range of riders.