Your situation is covered in IRS publication 463 which you should read thoroughly.
https://www.irs.gov/uac/About-Publication-463To summarize: Your husband can deduct travel expenses for temporary assignments away from his "tax home." If he has no tax home, he can not deduct travel. It sounds like he probably does have a tax home in WY, but there are several factors to consider, see publication 463.
If he can deduct travel away from his tax home, then he can deduct the cost of transportation, food and lodging. For transportation, you can not use the standard mileage rate because your vehicle is not a "car" under IRS definition. You need to use the actual mileage method, which means keeping a diary or other accurate records of all miles driven for personal and work, all gas and repairs. Then you deduct the percent of work expense based on percentage of work mileage. On top of that you can deduct tolls and parking fees. Turbotax will do this for you, but having accurate records is a key requirement for the IRS.
For lodging, he can deduct the actual cost of lodging. Since you have a camper, your cost of lodging would only be the camper fees you pay at each stop. You can't deduct the cost of the camper as lodging, because you will be deducting it in two other places. You will take a deduction for depreciation (wear and tear) in the transportation section, and you can deduct the loan interest as mortgage interest.
For meals, he can deduct 50% of the actual cost of meals, or 50% of the Federal per diem rate for meals. Publication 463 shows where to find the per diem rate, it is different for different areas of the country, so again keeping accurate records of where you went and how long you stayed in each place is key. In Turbotax you enter the full amount and the program will calculate the 50%.
Remember that if you travel with him it is important that you can not deduct your meals, and you can not deduct any personal travel or personal expenses, only work-related. If you take a few days off between jobs to sightsee, you can't include that transportation, food or lodging cost.
Finally, about employer reimbursement:
If he receives a travel stipend that is taxed as part of his pay, he can fully deduct his travel expenses as described above. If he receives a stipend that is not taxed, he can only deduct travel expenses that are more than the untaxed stipend. After entering all your expenses for transportation, food and lodging, Turbotax will ask if he received any untaxed reimbursement or stipend.
