An oral contract can be enforceable. The problem is that it can also be changed by actions prospectively (for the future), but cannot be changed after you perform the work. So if they agreed to pay $10.00 per hour. You work 10 hours and are due $100. But, if the employer says, from now on, you get $9.00 per hour. If you continue working, likely, you are earning $9 per hour. However, if the employer pays $9 per hour, when you had agreed that you were getting $10, then you remain due wages....
There may be additional issues in the LLC agreement that change the analysis for you. Often LLC agreements have language regarding who is liable. This language could alter the analysis in your case. You should get all agreement looked at together to determine the actual risk.
I am expecting that there are a lot more facts that are going on. You probably should try and get/keep copies of any written warnings and further document all conversations. Probably a good idea to start a log of all the actions, statements, etc. made by management and co-workers. You should also likely contact an attorney once you have gathered this information so that you can show them and explain your situation in detail.
Oregon is an at-will state. This means that you can be terminated with or without reason, so long as it is not a protected reason. (discrimination against race, religion, etc). This suspends future compensation, not compensation for work you already performed. If you have a problem with getting paid, look up a wage claim attorney.
Yes. Depending upon how you request it, and what you request, you could get one day's wage for each day they are late paying your wages. You have a misunderstanding about the limitation of the penalty wages. That limitation is only if they pay all wages within 12 days. You should contact an employment attorney who handles wage claims to discuss the best way to proceed. The difference in the penlaty could be several thousand dollars depending upon multiple factors including your wage rate.
Try and make an appointment to speak with an attorney before your meeting in two days. This way the attorney knows what is going on from the start and can help advise you through the process. There are things you want to do and things you want to avoid to assist your claim in developing properly.
If you can prove that any employer discriminates against you for filing certain employment claims, such as wage claims, there is a suit you can file regarding that as well. Also, if your former employer is providing false information to keep you form obtaining a job, that can be actionable as well.
You should contact an attorney. Likely you have a claim under the FMLA or OFLA. These are federal and state laws that restrict employers from discriminating against you because you take leave for medical reasons. Only certain employers and employees are eligible for the protection and it only protects against certain types of actions. Working at a jail likely means that your employer is required to comply, so you should discuss all the facts with an employment attorney.