^FPS problems can be solved only by increasing the game performance, lowering graphics and such, or maybe is just a problems with the execution of the game, which is mostly tied to your PC's compinents as far as I know.
Also, if I remember correctly, the first Dark Souls had a terrible launch on PC and some modders solved that issue, I don't remember what was the issue, bit some modders fixed it, so you can search about a mod that increases the performance of the game for PC, note that this problem appears only in the standard version of the game and not on the Remaster or at least, it should, maybe test a bit, you have nothing to lose.
If this didn't solve anything, there isn't much that can be done without an outside hardware optimization with new graphic cards, memory and such fancy stuff.
