For sure as it is part of your start up costs. Even if it is not, you can still deduct it as current expenses. Startup costs are subject to expenses amortization.
Check this link out for further details on this;
The following excerpt from the IRS website may shed further light on this issue.
"The IRS allows you to deduct $5,000 in business startup costs and $5,000 in organizational costs, but only if your total startup costs are $50,000 or less. If your startup costs for either area exceed $50,000, the amount of your allowable deduction will be reduced by that dollar amount."
A general partnership starts as soon as you agree to run your business together. No contract is needed for that to qualify you for a partnership.
DBA allows you to use any name for your partnership, it does not create a separate entity.
As for EIN, you apply for it after setting up your partnership. Once it is assigned, the IRS becomes aware of your partnership. You can apply for an EIN online here https://sa.www4.irs.gov/modiein/individual/index.jsp so you can file.
You will need to file form 1065 if there were any business activities including income or deductions.
Hope that answers your question