Handjob does not transmit any stds.
With the exception of some stds which spreads through skin contact. *But the likelihood is extremely low.
There are no STDs that are transmitted by handjobs. The STDs that are transmitted by skin to skin contact are things like herpes, syphilis and HPV, but those are genital to genital skin to skin contact.
1) The chances is near zero, if not impossible. I have told you negligible risk already.
2) what do i mean by extremely unlikely? Means practically no risk. Way lower than the chance of plane crash.
3) if u r so worried, go get a test and move on. I m sure u will be fine