About the last question: You do not need to use Portal for that, simply go to the AoW, change settings to Solo/Co-op and pick any mode/map you wish there. Then you can play solo (or with friends) there while all the other "players" are AI bots. Just don't be confused by the start of the round where it is looking for players for ten seconds - just wait until it ends and you can play solo. It works nicely, except the fact DICE have disabled any but base XP progression there recently (by their words, it's temporal, but nobody knows when it comes back). 🙂
About the Portal: You can set a maximum of players there and you can also set a maximum of AI bots there - you need to set them as PvP AI (in AI type setting), which can be replaced by human players when joined (the limit is driven by the max. players setting). PvE AI type are not being replaced by players (and the maximum is set by the PvE AI count setting).