You can currently change back and forth freely between the acts in the time skip, so you can go past the war content into the later acts if you feel like skipping that content.
The war against the undead of last update is after the preg/birth acts and therefore unrelated.
not, the war and the pergancy of multiple perso are not relate
but you have to make them pregnant.
there also a some number of scene recquiring multiple personnage to be part of your harem. Like a girl won't have her scene in the preg or the bith act because an another girl's rout wasn't entamed
