The way to calculate speed with towing a station is fairly simple: design the tug, and look at its speed and range.
For example, I have a tug that is exactly 50,000 tons, with a speed of 7200 km/s and range of 317.2 billion km
1. If I want to tow a station that is 500,000 tons, then I add the weight of the station and the weight of the tug together (550,000 tons in this case).
2. Divide the weight of the tug by the combined weight (so 50,000 / 550,000). In this case, it equals 1/11 (0.9091)
3. Multiply the speed and range of the tug by that result to get the towing speed and range: speed of 655 km/s and range of 28.83 billion km.
Edit: so your tug would have a speed of 1838 km/s and a range of 338 billion km, if your station is 72,000 tons
I think you can drop most of that fuel, unless you want to tow a 500,000 ton station 68 billion km in one go (and are willing to spend 5.8 years doing so)