I love this feature loaded great sounding player. The remote is an ergonomic masterpiece and lets me access so many features (e.g advanced zoom control!).

But how dumb that while it lets you teach it to control numerous brands of vintage TVs, including the TV’s volume control, unlike my Oppo BDP-95, it doesn’t let you control the analog stereo output level feeding my power amp (which has no remote).

Are there any universal remotes under $150. that can do this? And, if I ever wanted to add a pair of powered subwoofers, could the remote also control the player’s analog subwoofer output levels?

The analog audio outputs on that DVD player, are fixed. You can NOT adjust the level output on them.
This is the same as on most all disc playing machines. Has been this way since forever, with only a few weird exceptions here and there.

To do what you want, you need a preamplifier. But considering the cost, it maybe a better solution to just get an A/V receiver. Unless that power amp you are using is something special.