How can a President of an LLC use company funds?

There are numerous questions contained in your question. The IRS can challenge salary as being excessive and partly a disguised dividend. Normally expenses must be company related, unless a contract permits an officer/director/employee reimbursement for personal expenses as part of compensation, which would not be rare. If you are a member or a manager, you may have standing to sue for breach of fiduciary duty, but you will really need to be interviewed by a lawyer to see which of your complaints have standing and legally recognized damages and which don't.