You're fine using 5w-30.
My 94 also has a very faint knock but I believe its lifters. Its done it for 3 years now and hasn't changed (Over 30,000miles) so I'm not worried about it. The lifters seem to be getting progressively worse though. For a good year they stopped ticking all together but now they normally tick to some extent till the oil warms up. Sometimes its very very loud. Like you can hardly talk standing beside of the Jeep loud.
1994 ZJ-I6 w/216,000 mi
1998 ZJ 5.9 w/65,155 mi Slate Black
2004 KJ w/90,300 mi