Feed Manager is not broken, the feed generated by the forums is not resolving the url correctly. I can only fix the forum feed in the next release.
I do not have an immediate fix for that problem and credentials to your site will not enable me to solve it.
My advice is make a backup before you upgrade so can restore the previous version if something goes wrong. I am not personally responsible for your site.
The best I can do is fix the problem with the forum feed and make a new package available to you asap, possibly as soon as tomorrow.
I really don't understand why you cannot install it in the root of the IIS site, it makes no sense to me why you have it installed in a sub folder named website3. If you had another site running in the root it would make sense but since you don't and are just redirecting to the sub folder it makes no sense.