What is consider too low of thyroid antibodies and thyroid peroxidase? what is a good reference range?

Depends on the lab: Diffenent laboratories may use different methods of measuring a particular chemical which may not even be comparable. That is why you should always check for what that lab considers its "normal" range. They sometimes change their assay over time and if your numbers change a lot your doc should check with them about that possibility.

Levels not important: To see if your thyroid is healthy the only tests needed are a total or free T4 and a TSH. If they are fine there is no need to measure thyroid antibodies. If the TSH is high, elevation of one or both thyroid antibodies suggests you may have autoimmune thyroiditis which sometimes causes an underactive thyroid. Very high levels may indicate a higher risk but low levels are of no concern