Job with massively fluctuating activity levels, help?

Hi all! I'm still fairly new to this, and still trying to pin down my TDEE to a more accurate figure, but I'm really stuck as to what to set my activity level at. I'm about to go off on a bit of a background ramble, apologies, skip to the last paragraph for the questions!

I'm self-employed in the entertainment industry, and my job varies massively, some days I'm just sat at a console pushing faders for 90 mins, some days I'm humping quarter tonne boxes up ramps for hours at a time, and pretty much every variation of time and effort in between. It's quiet season right now, so I'm generally only working 3-5 days a week at the moment, but that varies from whole weeks off to working 7 days a week, in September - December I have very few days off, but the summer is weeks on end with no work. When I'm not working I'm getting to the gym and dancing, which I'm logging, but otherwise I'm pretty sedentary on my days off.

At the moment it's set to "Lightly Active", based on the fact that my most common working condition is spending 1-2 hours of moderate-heavy physical exertion, then 3-4 hours of light-moderate activity, then back 8 hours later for 2 hours of moderate activity. I have attempted to log particularly strenuous periods of work under the closest available activity (moving furniture, carrying boxes) but calories and time are all very sketchy doing it like this.

So basically, until I get my FitBit for my birthday, should I set activity to Sedentary and log *everything*, even though the calorie burn is probably inaccurate? Is "Lightly Active" likely to be a good average given the wildly varying activity levels on a day to day basis? Or is any attempt to second guess myself at this stage a bit pointless, and I should just play it by ear depending on results til I can measure more accurately?