Penny is shown to be completely useless when using glue, but in The Work Song Nanocluster (2009) (Season 2) she actually had a home business making and selling barrettes, which involved gluing the parts together, and she managed fine.
When Sheldon, Leonard, and Amy are shopping at the store, you can see Target's "Up and and Up" brand in the background. When they go around the corner you also see CVS brand products.
When Howard brings out the acetylene torch, it is not a torch for jewelry making. It is, in fact, a cutting torch and would be completely useless for making jewelry. In addition, there are no oxygen or acetylene tanks, both of which are necessary to operate an ox-acetylene torch of any kind.
When Amy makes tea for Sheldon, you can see her take a dry tea bag from the cup and set it on the counter.
During the last jewelry making scene, when Raj tells Howard he's upset at Howard for encroaching on Girls Night and says it's not about the jewelry but feeling comfortable enough to open up about his feelings, then Howard replies with "Since when can't you open up with me?" His mouth moves but the word "me" cannot be heard, just read with subtitles.
If Sheldon were looking for someone to rival Arthur Jeffries (Professor Proton) who has been established to have a PhD, it is doubtful he would choose Bill Nye, whose educational background is limited to a BS degree in Engineering, a field he does not regard as science or even worthwhile.
Sheldon tells Amy he's mastered the big three social skills (coy smile, friendly chuckle, and the vocalization of sympathy.) He then says the vocalization of sympathy is tricky and he's still working on it. If he had mastered it, he wouldn't still be working on it.