Yes. Using the extra entry tokens is a good idea.
You can always explain extra entrances thematically. Climbing in through upper windows or through a sally port and so on.
Indeed! While the other suggested entry on the castle is closer to being equidistant, I prefer to treat the one open window next to the blown up front door entry as an additional entry point for the front door team, because of theme.
When using 2 maps its also fun to join them thematically which can alleviate the issue of both teams starting right on top of each other in some cases. E.g. castle + catacombs connect through rear stone stairs and hole in the ground near Sneak secondary objective and/or secret doors hidden underneath crate tokens that you must search at castle action circles lead to the 3rd and forth suggested additional entrances in Catacombs, via ladders. Castle + gevaudan link up to an obvious front door entry (the castle entry being guarded by a nearby cabin outpost). But you can put secret door tokens in objective or action circles as alternate ways to move between the 2 maps.