For sure a letter like that could be used as evidence. But having gotten to the letter-writing point, you would already be at a stage of trying to...

What kind of penalties should i expect? is there anyway i can get off without jail time?

If your 2013 DWI charge was in Texas, then you could not have had it dismissed via deferred adjudication. There has been no deferred adjudication...

Will the police do anything? How long will it take for them to investigate or find out who it was?

Chapter 33 of the Texas Penal Code defines computer crimes. If you make a complaint with the police they should look into it. However, police...