Bitt is correct in that the ALT and release behavior is separate from real keystroke shortcuts or accelerators. It's a way to navigate the menu with the keyboard, while real shortcuts are single press actions that immediately fire and may or may not be linked with a specific menu command.

Instead of jumping through these hoops, get I think the best idea is to get back to the authors of this program and get them to put in some real keyboard shortcuts for the various options you want. If they're really keen on adding functionality for you ask them to allow editing of their shortcuts so that you can define or redefine your own shortcuts for any menu item. That way you can have sensible single press shortcuts as well, not something you have to stack up in a macro only to trigger a single function.

If their program currently doesn't work without releasing alt for any keyboard shortcut, then they indeed have a significant bug.