A: The real answer here is going to depend upon several specifics: the activity, the release document itself, whether you had any negotiation of the document before signature, the actions of the organization/individual who asked you to sign the release, YOUR actions, the location of the activity, etcetera.
Long story short, without knowing the specifics, a factual and complete answer is impossible. Sorry!
A: First, there's no specific "self-employment" registry. If you plan to operate a business in the state of North Carolina, you need to register with the Secretary of State. You would need to choose a specific entity form type (LLC, Inc, etc) and you would also need to choose how your entity would be taxed (some form types don't get a "choice" per se).
But as a self-employed person, many opt to create a LLC as a "disregarded entity" with the IRS. This means that you have a business entity, with an IRS-provided TaxID number, and the protections of a limited liability company. But from a TAX perspective, the IRS would "disregard" the business and simply tax you on the earnings of the business.
This can be of significance, so you'll want to talk with an attorney and/or a tax professional (CPA) about your planned activities and both your entity form type and your tax type so that you can optimize your choices.
If you were to be an LLC as a disregarded entity (a sole proprietor), then you would owe both the taxes on your FTE wages as well as self-employed taxes (at a tax rate determined by your total earnings) on the money from your side job.
So using round numbers, pretend tax rates and ignoring the concept of withholding, let's assume that your current federal effective tax rate is 20% and that you make $100K/year. You'd owe $20K in federal tax for your income. But if your side hustle also made $100K/year, your effective tax rate could creep higher (as an incremental tax, not every dollar is taxed at the same rate) to say, 22%, so you could end up owing $44K in tax.
Which might be fine with you... until you forget to pay estimated taxes throughout the year and the IRS then penalizes you for not paying them a percentage of your earnings throughout the year (whereas the withholding payments from your FTE job are typically seen as those payments).
All in all, there are a TON of considerations for doing this and it's not something you should just look online for free advice to fully answer.
A: Hi. Yes, it is both common and legal for an event space owner to hold a renter liable for damages caused to the space by the renter's guests. If you are concerned about your guests causing damage, it would be prudent to remove such guests from your invite list. Otherwise, you can always purchase event insurance to cover you in the event of some liability.
A: Forced? No.
Can they condition signature to receiving some form of severance? Yes.
Can they condition it to receive a final paycheck of money earned? No.
Can they include a non-compete in a separation agreement? Yes… but California has VERY employee-friendly laws related to non-competes. The specifics of the presented language in the agreement will matter and should be reviewed by competent counsel in your jurisdiction.
