Why don't you take some pictures of the door molding and potential gap areas to post here? That will help people weigh in. I have fairly large gaps on my 2nd floor doors, for example, where I believe that there was 1970s carpet. Those gaps don't bother me at all. Gaps on the door casement might be a problem, but I would greatly prefer filling that gap over leaving laminate flooring or replacing flooring. I would also think that laying reclaimed flooring over your original would require cutting still more off of your doors/casings.
I have done this trick a few times and it worked for me. In one house all the trim was cut short for carpet and we took the carpet out. I took a piece of door stop ( 3/8 X 1¼ X ?) I cut this piece down to ¼" wider and ½ longer than the short base. I rounded the 3 edges and slipped it under the short trim. When I got it to fit perfect and the perfect color, I put a spot of glue on the floor and slipped it into place. It took care of the gap and looked like it was part of the trim rather than a mistake. I can't think of any other thing short of inventing a wood stretcher.
Without seeing pictures of the molding, it's kind of hard to offer any advice. Regarding the doors, Your problem depends on how big of a gap there is between the bottom of the door and the existing laminate. If the door is fairly tight to the existing floor, another 1/4" shouldn't be too big of a deal aesthetically. It's not unusual to have a 3/4" gap between the door and hardwood.