Will this slow my case down?

If anything, this might speed up your case.

How long do I need to be out of the usa before I can return on a B2 tourist visa ? I am a UK citizen

6 months in the US, followed by 5 months out of the US, followed by 1-2 months in the US should work. BUT, if you could do closer to 3-4 months...

Can I Apply and get food stamps for my American son ? I just got my green card .

Not a good idea. They look at household income and assume that you will be eating some of his food.

This is not an immigration question. I have re-classified it.

J1 status date in form I-129?

You appear to have put the correct information on the EMPLOYER's I-129 ... keep in mind that those papers are not your property.

You are inquiring too soon ... 4-7 months is more normal.

GC renewal when child turns 14

Your perspective is a bit confusing. Are you asking whether or not your 14 year old child can travel internationally?

It can depend on which Consulate you're dealing with. But, my colleagues are correct with their general estimate of 4-6 months.

What if I divorce while i751 pending?

Get an attorney and fight the divorce. As long as it isn't final, you remain married.

Don't be lazy and don't play games with governments. Go home and get the certification.