ESR will ever start, if you do it this way and insert a DVD-Video, or patched disc, in PS2-Browser/OSDSYS.
FMCB may interferer with it, because it has some problems, when you try to boot a disc from PS2Browser.
Can you try to embed ESR to the "BxEXEC-DVDPLAYER"-Folder, before installing FMCB and test it on a NoMod-PS2?
Your guesses are right.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux