So I picked up my new bike (Scattante CFR Comp 58cm). I took it out for a quick 1 hour ride today and made some tiny adjustments to the seat. It seems to fit really well but the only issue is since I had to move the saddle back a bit the shifters are further than I would like.

While riding I kept moving my hands back to alleviate slight back pain I was getting and slight numbness in my hands.

Unfortunately the lower size to 58 is 55 which would probably be too small since I'm 6'0'' - 6'1''. I would have to get a completely different bike which would be a PITA.

I'm wondering if changing the stem from a 120mm to 100mm or even 90 might fix this issue I'm having?

Current stem details:
Alloy, ID: 28.6mm, -5 degree, Bar bore: 31.8mm, Length: 120mm(58/61cm)