Youtube – way to disable or redirect the youtube ‘home’ button

Firefox add-on SmartVideo for YouTube will do just that. You can even tell it to either start the video when you want. You can just open the link in a new tab, and just come back to it when you're ready to watch the vid. It has other useful options as well.

Edit: SmartVideo can be a bit buggy. As to 720p videos being buffered, I think it's because all videos in 720p (or higher? not sure) are already on WebM format. It's my default setting. It's the fastest video setting to load, faster than a 480p flv file.

Edit2: SmartVideo is also available for Google Chrome: https://chrome.google.com/webstore/detail/smartvideo-for-youtube/lnkdbjbjpnpjeciipoaflmpcddinpjjp?hl=en

No, suggested videos work off the user's Cache or Google account. YouTube looks back on past videos watched by the user and randomly generates suggestions for them. Although, it is possible that one or more of your videos will be suggested more than once.