Hello,
the problem with the TAB for editing e.g. language (#4) can be solved by changing the stdmenu.cfg (see /usr/lib/refractasnapshot/iso/isolinux). Could be, that the problem appears with debian based snapshots (devuan based seems to b no problem according fsmithred). My idea was, to check the stdmenu.cfg of debian and there are some changes. I changed the refractasnapshot stdmenu.cfg with these debian entries (all other entries concerning the menu color are unchanged):

menu vshift 8
menu rows 12
menu helpmsgrow 14
menu cmdlinerow 16
menu timeoutrow 16
menu tabmsgrow 18
menu tabmsg Press ENTER to boot or TAB to edit a menu entry

After running refractasnapshot with these changes in stdmenu.cfg, editing seems to be o.k. I've used the newest refractasnapshot from the devuan pool (fsmithred's link). Hope, that helps, but not sure.