Slow internet/gaming speeds at night?

I am embarrassed to say I have Time Warner Cable's ****** internet plan at 30 download 5 upload speed. I absolutely hate this company for a lot of reasons but I don't have a choice considering my only other option is Verizon with a maximum of 2 download 1 upload speed. TWC throttles and I can prove it but that is a whole different story. Anyway my internet and Xbox Live is beyond slow from 7pm to Midnight then I get my normal speeds again. I know that these are during peak hours but the speeds I am experiencing is just ridiculous. I am not just basing the slowness on speed tests believe me I know how unreliable those can be. I am basing it on what I am seeing. I have been dealing with this problem for quite some time now and I am just getting so fed up with customer service being absolutely no help so I am desperately looking for some help here. I don't know if there is anything I can do from my end but to help out in any way I can here is my setup.

Note: I do not use wireless, everything is wired.
- My own Motorola SB6121 modem (TWC's modem's are even slower so I bought my own)
- Connected to the port is my Linksys WRT54g v4 router with DD-WRT firmware
- I have my Computer and Xbox connected through my lan ports
- UPNP is enabled (Port forwarding xbox ports or using DMZ does not fix my xbox live lag issue)

Any help would be greatly appreciated. I don't know what else to do seeing as I cannot switch ISP's