Loading only position stuff etc from a txt file in combination with level_load will ofcourse be a bit simpler to make but do keep in mind that won't allow you to save e.g. summonings or 'spawned from script/ent_created' enemies (so only pre-placed enemies). If this doesn't bother you than by all means go for it.

As for you door positions, iirc you can attach an other entity in WED in entity edit/properties menu (look for something like attach or parent or such). You can than use it in script. If that doesn't work out or if you need more attachments, save the ID's in skills of the door ents.

And get well soon