Finally, the Histeria forum helpfully published each member's IP address underneath their user title. Looking at a selection of Sweet's contributions, they all appear to be from a range starting 216.152.44.
https://archive.is/XNK7e - 216.152.44.77 and 216.152.44.125
https://archive.is/g0uT1 - 216.152.44.175
The IP range in question is located in Aurora, Illinois:
https://archive.is/Hamkt
Are blocks of IP addresses periodically reassigned? If so, it's possible that in 2002 the IP range was used by an Arkansas or Missouri ISP. However, Sweet has repeatedly said he was born in Chicago. It would thus be unsurprising if he had family in that part of the country, perhaps in Aurora.
Could Sweet have been living with a relative in Illinois in 2002?