I apologize for the delay. Wasn't around a computer
(1) I did not mean to alarm with my previous answer. You asked if it was possible, and yes, it is possible. However, that does not mean it is easy to be charged or convicted.
(2) You would not be indicted simply because he mentions your name. The government would look for additional evidence tying you to the crime.
(3) Yes, accomplice testimony needs to be corroborated although not everything he might testify to needs to be corroborated.
(4) Having not seen the emails and texts I cannot say whether they help or hurt you, but assuming do not suggest doing anything criminal
they should help you.
(5) On that type of crime not being present is not that determinative. You can direct someone's activity from anywhere in the world.
(6) It is very easy for me to say don't worry. I realize it is more difficult in your shoes. I believe it is very rare for people to get charged with crimes they did not commit. If this person implicates you, I would expect the authorities to investigate you, but given that you were not involved they should not find anything that backs up his story and the available evidence should corroborate your version of events. Assuming that is the case the chances of you being indicted are very slim.