I have a few fixes to your problems.
1st for those who screen isnt big enopugh so you have to scroll to see the whole threaad.right click on your desktop go to properties then click on thesettings tab.Then look for screen resolution and you are probably on 800 by 600 at the most. Probably lower if it is lower then 800 by 600 then chnage it to 800 by 600 and hit apply.I use 1024 by 768 you can try this but some older comps may not be able to handle it as well.Try this and see how it works.I have the brown lines on the side as well.I will work with my adjustments I can make and see if I can fix it.Will let you know if I find a way to stretch the forum section.
As for the slow loading it should start being faster now that you have used it after the first time.Your comp will save the general page and smaller changes in it like posts will load faster now.So it should only load slower for your very first time using the forum.If it is still loading slow let me know I may be able to help you speed things up a tad.
As for the new forums I like them the looks are more natural for hunting style forum. Great colors and layout.