Engineer for TN visa

The engineer designation for TN visas seems to be rather vague. I have an offer to work as a project controls engineer (planning, scheduling, etc.) for a company in Houston, and I have 7 years documented experience as a project controls manager working in Asia as an expat. My Canadian degree is in mechanical engineering.

Questions are:

1. is the job title mismatch too far off?
2. are copies of employment certificates stating dates and position held sufficient?
3. should the letter from the employer stress a need for knowledge of mechanical engineering, or should it focus on project controls?

Unfortunately my cases isn't as clear cut as a mech engineer going for a mech engineering job.

Would appreciate hearing from people with similar experiences or knowledge of this type of engineer case.