First, you need to determine if any of your lodging and transportation costs are deductible at all. It depends on several factors, most importantly where is your tax home, and is travel away from your tax home temporary. See publication 463, chapter 1.
https://www.irs.gov/forms-pubs/about-publication-463
If you travel away from your tax home on a temporary assignment, you can deduct travel and lodging expenses. Your trailer can be a lodging expense. You could deduct actual expenses of ownership, including interest and depreciation, as well as fuel and maintenance, if you keep the correct type of records. This is covered in chapter 1 and chapter 4 of publication 463. In addition, you can deduct lot fees.
Temporary means expected to last, and actually lasting, less than 1 year. Travel is not deductible for indefinite assignments, and travel is not deductible if you have no permanent tax home.
Another point, your transportation and lodging is only deductible if you report the $150 per diem as part of your gross taxable income (which you are required to do). Your actual cost might be more or less than the per diem, you simply report your per diem as taxable and then you deduct whatever you actually pay, whether it is more or less than the per diem.
