1. Do we need to generate 1099 form for each contractor or people working for commission for me? Or only if the payout is more than $600 in year.
2. Do I need to file 1099 for Paying to Non-US Companies or contractors for their services? How IRS expects expenses paid for services taken from companies abroad?

3. For a Husband/Wife Partner LLC, after calculating total income, LLC should file 1065 & issue Schedule K-1 to Partners, based on their percentages?
4. Partners will have to submit 1040 on their incomes even if they file taxes as “Married filing jointly”?

I will tackle #1. A 'contractor' (who gets a 1099) may or may not include 'people working for commission.' There is a long IRS list defining a contractor. It does not include anyone working on your premises, just for starters.
I know a small business who paid everyone on contractor basis and was penalized retroactively for years, all the payroll taxes, plus fines and interest. And none of them even worked on the premises, but they used equipment supplied by the company.

The minimum needing a 1099 is still $600 for the year.