I have had no such issues. Also, no other control issues whatsoever regarding playing the game using just a keyboard and a mouse. BTW I own the original CD version of this game and have spent over the years more than 100s of hours playing this one.
If you run into any issue that you think is related to mouse acceleration, the first thing to do should be to disable (minimize) this via Windows. Then, pick a mouse DPI and rely on the mouse drive (if you have one) to increase the acceleration to an acceptable level and use the game's build-in menu to fine tune it a little bit. If you have a dedicated mouse driver, you should always rely on that for fine tuning the mouse. If not, work with both Windows and the game itself to adjust mouse acceleration to a comfortable level.
Using a 2-button mouse with no further features is not easy if your goal is to play a FPS game *competitively* (not casually). Playing FPG with a mouse is very different from with a game controller. With a mouse, you most likely have to struggle with accuracy when scoping and sniping. However, Far cry 2 can be played just fine even with a crappy but fully usable mouse that has max DPI < 1600, as well as a mouse set to run at 25,600 DPI like the one I use for FPS.
It looks like you come from a console world. If so, you may want to consider buying a "cheating" FPS mouse for gaming on PC. It's a decent, cheap alternative to any overpriced expensive FPS mouse. A cheating mouse for FPS games can give the player unusual advantages for free. One such feature is to reduce DPI while the player is looking through a scope. This can greatly raise the accuracy of sniping. With this enabled, getting a head shot can become a piece of cake. Another feature is give the player the ability to do multi shots with only 1 click. The mouse driver will take over and simulate the player rapidly firing 3 (or 2 or 4) shots without the player's further actions. Such a mouse can make a mouse-based gameplay easily more enjoyable than using a controller.
If you just want to raise the accuracy of your aiming with a mouse, the easiest way is to play the game at 720P in full screen on a 120Hz or higher gaming monitor as big as you can get. This is an old game, you don't need to run it at high res like 4K.
Have fun!