I'm having a similar drama with Woking in my game. What I've done is looked at months where I've had a normal flow of games (so no major cup-ties) and did an expenditure review. I compared that with my average income based on that flow of games.
Based on that info, I was able to target what my wage budget could be and allow the club to break even through the course of the season. As I've not finished a full season yet, I've got no idea what the off-season brings in terms of cash.
At the moment, my club is slated to break even for the season without Cup matches. Luckily, I've had a bit of an FA Cup run, made it to the third round for a home date with Blackburn and amazingly we drew so I got to go back to ewood for a serious pay day (we lost). As a result, the club should be substantially in the black this year. However, I'm not factoring that into my budget forecasts from a management perspective - I don't want to end up like Leeds, budgeting in Champions League money.