Changing job -Social Security-Family reunification (non-EU)-pregnancy

Hi all, forgive me for creating a new thread. Since most of this information is probably scattered in a lot of different threads and forums. My current family situation is kind of intertwined with these topics. I just simply ask for advice if someone has some insight.

Here is the story:

I (non-EU), recently (November 2022) just moved to Belgium from Germany for the purpose of employment (permanent employment/without time contract). I currently hold a single permit. I also have a permanent residency in Germany/Niederlanssungerlaubniss (not permanent EU/daueraufenthalt-EU), which I converted from EU Blue Card previously. I also have paid for more than 4 years of social security in Germany for full-time employment, in case this information also changes something. I married (also) a non-EU national in the summer of last year. My wife initially came to Germany under a visitor visa (90 days). The initial plan was to help "us" to move from Germany to Belgium first, therefore she didn't immediately apply for the family reunification visa directly (but instead with the visitor visa). She was also here in Belgium for a couple of weeks before her visitor visa period expired.

Long story short, my wife is pregnant. We went to the doctor here in Belgium. She also received her INSZ number from the doctor (instead of from the city hall, I was also quite surprised, apparently doctors also have the authority to give this "temporary" national register number), in case this information is also useful later on. Just shortly before Christmas, she went back to our home country, and on January 2023, she applied for and submitted her family reunification visa. We can track the application, and it stated that the application has been submitted on 10 Jan 2023, registered by the immigration office on 21 Feb 2023, and is still being processed until this day. We need to give up our initial plan to deliver the baby here in Belgium because we decided ourselves that she will not fly (long distance) after reaching 33 weeks of pregnancy period (even though airlines permit it up to 36 weeks of pregnancy period).

To be honest, we expected her visa will be issued about one or two weeks ago (since that was the average waiting period for another non-eu applicant as well based on this expat forum for the last couple of months/years), for complete and perfect files (our files are perfect, only proof of rental contract by myrent.be has sent separately via Email later on to ibz because when she submitted her files from the embassy in our home country, this proof wasn't available online yet. But at that time, she included our rental contract signed by me and my landlord). We also attached a confirmation from the doctor in Belgium that she is pregnant (including the expected delivery date, which is at the end of June 2023). I also completely understand that by paper, the immigration office has the right to decide within 9 month waiting period for non-EU applicants.

To make things even more complicated than it already is, I apply for another job recently. I also realize that my current single permit is tied with my current employer and if I do really want to switch the job, I need to redo my single permit process (therefore, for my wife's application as well [?]).

I wonder, is our child will be automatically granted/not granted the visa as my wife (with the basis of current immigration law), or we will need to redo the similar process as my wife, but this time will be for our kid after she was born (which then I expect, we still have to wait for the decision for another more than 3-4 months after she was born, after making a passport for a newborn baby, collecting the required reunification documents of a minor child, and apply the reunification process)?

Do I have the right to take parental/paternity leave in order to be able to present there when my daughter is born?

What will happen if I decided to switch jobs, and re-apply for the single permit process to be able to work for the new employer?

What will happen if I quit my current job, fly to my home country in order to be able to stay there for a longer time, and end up with some gap between my current employment and the next employment? Is there will be an illegal period when I will not hold a valid residence permit? (I don't really care about the gap period relating to applying for permanent residency in Belgium in the long term)

Can I enter the EU with my current residence card in case I will enter during the application of the single permit process of the new employer?

Can I enter the EU with my Niederlasungerlaubniss from Germany?

Can we claim for birth allowance and child benefit? Under what conditions we can claim it? to whom? Belgium/Germany?

Any insight/advice will be highly appreciated.