it will definitely help a good amount, but it will still be a bottleneck. definitely worth the upgrade if you cant afford a mobo change with at least an i5.
I would not bother with a FX upgrade. Even the strongest one would severely hold back a 1070. The only REAL fix is to upgrade your cpu AND motherboard to either current Intel or wait for AMD to release Zen in a month or two.
you may need to repurchase windows if you bought the oem copy.
it can be costly to upgrade. the 8300 might be a good option depending on your budget. i could shave $100 off that if you want to cut out some features and overclocking capability. that list above is just what i recommend.