An easy way to reduce the liquid volume is a base step, base with NaOH, let settle and decant the liquid, a couple water washes help clean things up, then acidify and add water to get an appropriate volume.

ime you need 5-6 boils + pressing the liquid out of the seeds between boils to get everything out. Freeze/thaw cycles before or inbetween boils helps. 5 mins microwave boils is the fastest approach but there's a risk of overflowing and dealling with scorching hot jars.

50g is a perfect amount to work with imo. The seeds swell and becomes bulky when working with bigger amounts. It should net you 3g freebase or 3.5g HCl salt.

The most critical part of a rue extraction to me is preparing the tea.