You could try going gloveless for a ride to see if it makes a difference. I think it is unlikely but conceivable that a poorly placed pad could restrict blood flow in your hands. How long has this been happening? Sometimes changes are coincidental, so don't immediately jump to the conclusion that a change to your setup caused this. Sliding your seat back would normally improve your situation rather than hinder it. You can try changing things back one at a time to see if any of them improve the numbness. It could also be a medical issue that no amount of adjustments to your bike will solve.

One more thing to hopefully help you better visualize what is going on with seat position. Imagine standing on a flat surface and bending your torso at a 90 degree angle to your legs and keeping your legs at a perfect 90 degree angle to the ground (forming a perfect upside down L). If you didn't have anything to support your body you would end up falling on your face. Now imagine moving your butt back to the point that your butt is behind your heals. Eventually you will slide your butt far enough back that you will be able to balance without falling on your face. That is effectively what you are doing by sliding your seat back. You are changing your balance point to putt less pressure on your hands. Being too far back can have a negative impact in other areas, so you want to find that perfect spot that allows you to be far enough forward without smacking your face against the bike. Some people suggest putting your hands in the drops, then take your hands away to see if you can hold the position without bobbing or falling forward. The furthest forward position that allows you to do that should be very close to the ideal position for your saddle. Keep in mind that this can change from saddle to saddle, so don't expect it to be the same if you change your saddle in the future.