It'll be easier to explain if I have the files that you merged. Just zip all the IFOs and the last menu vob (VTS_0x_0.VOB), and attach it here. Only the Pro version can customize to your needs.
According to the guide on site, just follow exactly as is. Since your custom menu has 6 buttons (I assume), be assure that all button commands are LinkTailPGC, exactly like the original
dvdremake menu. Some command editing is required to do what you want.