I have just skimmed this thread very quickly, and did not see any mention of capturing the JD ether separately from the other ingredients before mixing it into the final blend.

The straw method does allow milking the contents positively and safely, but directly into the measured oil and kero? I can appreciate that that would foam, spatter and likely waste some ether volume. I use a separate catch jar.

I use one jar with two caps available. One cap is intact, to seal the catch jar. The other cap has a punched hole only slightly larger than the straw. The restricted hole in the one cap reduces loss of the ether, while venting the propellant away nicely. The catch-jar has a mark at the approximate level of liquid ether needed for one liter of fuel. When that mark has been generously reached, stop spraying, and switch to the intact cap.

What remains in the JD can will be there next time you need it. Pressure may fall off to where you can safely punch an awl through the rim and pour it directly into the catch-jar at the start of that blend session.

Don't expect the closed jar to keep the ether very long; pour the ether into your fuel batch within minutes of drawing it from the rattle-can.

I store blended fuel in metal cans, with the cap threads wrapped in plumbers' teflon thread-seal tape. Also. I have prepped the can caps by soldering two copper tubes through their tops. One gets an extension down to the bottom of the can. The other projects into the can less than the height of the cap rim. Long tube is the 'fill' tube; short one is the 'vent.' A few inches of black neoprene connecting the outer tubes holds seal very well over protracted time. This reduces the 'open to the atmosphere' time, thus involves less degradation of the fuel.

Just be sure to undo the vent tube first - residual pressure in the can may squirt fuel quite a distance.