221 g for H1 B (TAL): Apply for H4

I am a full-time employee at the good company. My petition for H1 B (academic) is approved and recently I visited India for stamping and currently stuck with 221 g for TAL (security clearance) as I am a PhD in Bio-science. Meanwhile, my employer has terminated. I am trying to talk to them if they can reconsider their decision. I want to go back to US to join my family, I just want to check what are my options. 1) My spouse is on H1 can I am eligible for H4, Can I apply for H4 stamping while H1 B 221 g is pending, or do I have to withdraw my H1 B application before applying for H4.

  1. What are my chances of getting H4 approved, my spouse in US ( I140 approved) and kid ( US citizen)3) Can I get 221 g for H4 visa also as I am a PhD?4) Does withdrawing H1 B application can affect chances of getting H1 B in future