Gtx460 new buy request

First of all,definitely upgrade your monitor if you want to get a 4670,because GTX 460 on a 19" monitor(which mostly have a resolution of 1440x900 or 1280x1024) is a waste.
As for your questions
1_Yes
2_It depends on the games/resolution that you play.Most games are VGA limited, so there won't be any problems with them,but some are CPU-limited(like SC2) so you'll benefit from a faster CPU in them.
Also when you play at low resolutions like 1280x1024,games benefit from the CPU too,whereas if you raise the resolution and add some eye-candies like AA/AF,the game benefits more from VGA.

i played starcraft 2 at high settings at 1440x900 and i get 30-50 frames which was very smooth for me and i dont think it was cpu bottlenecked, only it lagged when going to ultra (not by much really) frames 18-35, so i think it is graphics card limited not cpu, but starcraft is very well optimised i think what i will upgrade for is metro 2033 as i can hardly play it at 1280x720 - high settings with frames 20-30, so what do you think ?

Your setup can handle SC2 fine, but if you add many units on the ground,you'll see the performance may drop(because of the CPU)
For Metro,well its a very demanding game and also not very optimized,that's why you can't max it out,upgrading to a GTX 460 will help, but i don't think its worth it to upgrade just for one game, because aside from Metro and few titles, a 4670 should play games fine on 1440x900.

If you aren't going to upgrade your monitor any time soon an HD5770 would be a more reasonable choice for an upgrade.

i have thought of the different choises but i have found 5770 for 210 USD where i live, 5750 for 190 USD and gtx460 768mb evga superclocked (equivalent to gtx465) for 240 USD so the small difference in price will give me a big difference in performance between 5770 and gtx460, and for 4670 it has been with me for 2 years and this is the time for graphics card change so not to be worried about system requirements for any coming games for another 2 years, as i change the graphics card every 2 years and the processor every 3 years (still 1+ year for the processor   ).