I live in South Carolina and going through a divorce, relocation clause

So - negotiate the settlement. You may want the help of a local attorney

Is company subj to MA Health Ins laws if workplace located in MA, registered in MA, headquartered in CA and incorporated in DE?

The Massachusetts health care regulations make the Affordable Care Act look simple. But this isn't a divorce question - try health insurance.

Where to file for divorce and keep custody of son

He has to file either in the state where she resides or in a state in which he has residency. If the child resides with her it would be prudent to...

Not likely. But you can consult a local attorney and discuss the situation in detail - see if you have more with which to work.

In a divorce who owns items I purchased with gift monies?

These are divided by negotiation - unless you're claiming that it was money from gifts specifically for you.

What do I do from here?

You can seek modification through the court.

In verified answer, besides admitting/denying the 1st 8 paragraphs, should I admit/deny the relief requested by the plaintiff?

As previously noted that is not the correct way to respond.

In affidavit in opposition to pretrail motion do I have to deny the Plnff's orders only or I can also address affdvt in support?

yes. However, motion practice pro se is not something that has a high success rate.

Turning 15 year old stipulation of settlement into judgment of divorce

The attorney isn't the important one. The spouse is. Can you get the rest of the necessary documents?

Divorce

That will not likely be the deciding factor. But you should consult a local attorney and discuss your issues in detail.