EV, EBITDAX, and FCF formulas for E&P Companies

Hey quick question for those with experience in valuation within the E&P industry.

I know the simple formulas for the above; the formulas I assume that the non-practitioner uses. My question is whether the following are more realistic, and used on the job.

EV = equity value less Cash & Cash Equivalents, less Net Value of Derivatives, less Investments in Equity Companies, plus Total Debt, plus Asset Retirement Obligation, plus Capital Leases, plus Unfunded Pension Obligations, plus Preferred Stock, plus Noncontrolling Interests.

EBITDAX : Operating Income plus DD&A, plus Asset Retirement Accretion, plus Stock‐Based Compensation, plus Non‐Cash Derivative Losses, plus Impairment Charges, plus Other One‐Time and Restructuring Charges, plus Exploration Expense.

And for FCF do you guys define it in terms of Discretionary CF less Maintenance Capital Spending less Dividend Payments?

I got the EV and EBITDAX formulas from BIWS O&G quick reference; but as I'm getting familiar with E&P financial statements these formulas make sense, and I am wondering if a recruiter would be impressed if answered this way.

Any help is appreciated.