1) Take v-sync off
2) I don't think 1440p is supported
3) Poorly optimized Unreal 3 engine. Almost no one plays with full-on nerdgasm graphics because it prevents us from experiencing pc master race 120fps
DirectX9 from the beginning was created before multicore or even hyper threading existed. Therefore DirectX9 is single threaded, thus only ever truly utilizing one CPU core. There is a multicore enable bit-flag in DirectX9 but even Microsoft themselves have stated it's only there for developmental use and hinder's pre-existing performance heavily. So much so that it's entirely counterproductive to use it, as CZeroFive said, the move to DirectX11 will open up GPU resources better, since DirectX11 is inherently multithreaded, there for keeping the GPU properly fed with data.
1440p is natively supported, same with 4K and even UHD and ultrawide, it's just the UI is not compatible with the resolutions larger than 1080p.
Unreal Engine 3 itself isn't really poorly optimized, it's the API behind it, there are many, many DirectX11 based Unreal Engine 3 games that run beautifully, but the DirectX9 ones have the same woes. Poor performance due to the lack of multithreading and multicore usage. Besides, Unreal Engine 3 is known for having a framerate cap built in by the men and women over at Epic Games, for network play which is 90fps, you can bypass it by using the Smoothed Framerate settings [bSmoothedFrameRate T/F MaxSmoothedFrameRate XXX], but it causes weird glitches and other stability issues. It's a cap put in place by Epic to stop garbage data overflow to the server. I myself have had issues staying connected to games with SmoothedFrameRate on and MaxSmoothed set to 240 which is my monitors' refresh rate. I'd rather stay locked to 90, then used SFR and get kicked after 5~6 minutes.