H1B extension question + Company switch


Here’s my situation,

I’m on an H1-B Visa with the stamped expiration date of 5-Jan-2019. My PED/I797 and I94 validity is more than visa at 20-Sep-2019. I understand different dates are possible even though they are unusual. I believe it was because I had gotten a 221-G form and I had to wait around a month to provide additional documents before my Visa was stamped. Now I plan to visit India sometime around June end for a week for personal reasons however I was also looking to switch companies before my visit, ideally in May or early June.

Considering I switch companies in May and my petition transfer/extension gets filed right away, does that mean I have to get new stamping done while re-entering? I suppose I have to but it’ll be nice to have someone confirm because there is a chance I might get a 221-G form once again and I wouldn’t want to wait in India when I just joined a job back a month ago.

More importantly, say if I don’t switch companies until I re-enter the US, starting first week of July, how does that affect my petition extension? My PED is in Sep-2019 but visa stamping expires Jan 2019 making July 2018 exactly 6 months prior to it, should the renewal process start with visa date in mind or the PED? Because that gives little to no time to switch and I’ll end up having to stay with my current employer.

I apologize if the situation is a little confusing but I can elaborate more if needed. I’ll be grateful if someone can help me out here. Thanks.