That "Inside the LEO Doghouse" article you found is a very good one. It's written by a guy I kind of work with and if you didn't read the whole thing, it's worth taking the time to.
Open expander cycles can still be very efficient. You can get Isp with LOX/LH2 up in the vicinity of 450 s, which is only a few s below RS-25 & RL-10.
You have to ...
I noticed between the info in the question, additional info in comments, and an assumption of 0.0 delta thrust at 0.0 flowrate, there was enough information to draw a exponential curve for the throttle.
Delta Thrust (N)
Inert Prop Flowrate (kg/s)
Using this throttle characteristic curve, I ...
The RL10 has been experimentally fired on methane and propane as well as hydrogen. This did entail modifications to several components of the engine; for the methane version:
Fuel component modifications were unique and were accomplished under the contract; assemblies that were changed were the pump, turbine, thrust control, injector, and thrust chamber.
An exhaustive 42 seconds of googling reveals this on Stellar Exploration's website:
As part of early R&D for a NASA funded deep space nano-satellite mission we have designed, built, and tested a miniaturized hypergolic bipropellant thruster. It provides 3 N of thrust with 285 sec specific impulse. The propellant is pressurized with gear pumps, allowing ...