Looking at the Lyman cast bullet handbook they are showing 5.0 gr. of 700X pushing a 41 gr. 225348 at 1872 fps at 25k CUP and 6.6 gr. delivering 2187 fps at 40k CUP. So a charge weight in the 3.0 to 3.5 grain range ought to get the velocity that you are looking for. I'm a believer that powder charges for reduced loads should be such that a double charge can't fit in the case or pressure safe should a double charge occur. I've used a case full of Trail Boss and a cast bullet in my 22 Hornet for fun, but if I recall it was still above 1100 fps.
Going this route I would think that a plain base 22 caliber cast bullet would be optimum, as placing gas checks on these bullets is a chore and they aren't needed for the application. A mold similar to this:
https://noebulletmolds.com/site/shop...2-4-cavity-pb/
would be what I would be looking for.
However, unless you really want the fiddle factor, the price of 100 rounds of 22RF ammo is about the same price as 100 SR/SP. Personally, as much as I find satisfaction casting and shooting my own bullets, I'd be looking at the 22 RF option as the best path forward.
Just in case you are wondering a 222 case holds about 8 gr. of Trail Boss to the top of the neck.