The dismissal with prejudice of your first suit only precludes you from bring those claims, and any others that you could have brought at the time. Because the conduct occurred after the dismissal, you would not be barred from bringing the claim.
For now, it will remain a cloud on title. The law regarding mechanics liens are very detailed, and require strict compliance in order to be valid. If it is valid, you can still defend based upon the complaints that you articulated. Your options are to sue them to quiet title (and for the poor workmanship) or wait for them to sue to enforce their lien, and defend (and counterclaim) on the same grounds. The contractor must file suite within 2 years from the completion of the work, or the lien...
The enforceability of an auto-charge provision comes down to proof that you agreed to the provision, and whether you properly provided notice of your intention to terminate. You can argue that your emails were sufficient to terminate. $6k is an atypically large amount to commit on a auto-renew basis. Depending on how clear the auto-charge provision was set forth, you may also gain leverage by asserting or threatening a claim under the deceptive trade practice statutes in CA and NY. You...
If and when you do decide to form an entity through which to conduct your business, consider a corporation with an IRS subchapter s election. For a simple structure like the one that you have described, an s-corporation is less expensive to organize and maintain than an LLC, and offers the same flow-through taxation of a partnerships or LLC.
In the absence of a good faith dispute as to whether he, in fact, owes you the money, your trainer's trainers attempt to condition the return of your $385 on new conditions likely NOT enforceable even if you do sign so as to get your money back.
If he is competing with the business, you can also bring an action derivatively on behalf of the company to get damages (which would go to the company, not you personally) and/or to have company dissolved. Courts often will order the corporation to reimburse litigant for fees incurred on its behalf.
A judgment creditor who serves a citation is entitled to discover non-exempt assets of the corporation, and demand a turnover of those non-exempt assets to satisfy the judgment. The citation is a lien against the assets of the company. A filing of a bankruptcy petition by the corporation will not only stay the citation proceedings, but if the citation was served with 90 days prior to the bankruptcy, the lien can possibly be avoided as a "preference."
You can manage the credit risk associated with any tenant by: 1) requiring advance payment of final month(s) of lease term; 2) requiring large security deposit; and/or 3) requiring a guarantor of all financial obligations, including liability for holdover tenancy.