[How to see which payoneer account is connected with my fiver account]

You can check your payoneer account. There is a option called “Funding Source”. You can see your fiverr user name there.

[How to embed a gig into my website]

Hi, You can’t embed your gig on your website. But you can embed your profile on your website. One thing I can suggest to you create a custom offer for the gig you want to embed. Then embed that custom offer on your site.