xps13 win10 generally slow and stuttering mouse movements

I bought a XPS13 back in June 2015a and am not happy with it at all. There seems to be a constant lag/stutter. Have been through this with Dell support a couple of times but they don't seem to be able to assist.

So I am thinking of doing a clean install of Win7, currently using Win10 upgraded from Win8. Win8 came with the purchase.

I am wanting advice on a couple of things:
1. Will I be able to install a new Win7 without any of the Dell stuff?
2. After installing Win7. Can I just go to Dell's website and download all the firmwares for this particular model?
3. I also bought MS Office 2013 with the purchase of the laptop. It is an OEM license. Can I install Office again and use the license?

Hope to hear back. Thanks!