preface every selector with .categoryname, so instead of
.topic-list td {
padding-bottom: 10px;
}
you have
.categoryname .topic-list td {
padding-bottom: 10px;
}
you can discover the .categoryname of a category by viewing the topic list in that category and inspect the source. The main <body> tag for that page will have a class like “category-foobar”
EDIT: Ah I missed that there was custom JS. That’s outside my knowledge I’m afraid!