A: No, quarter inch gaps would not be considered normal. Gaps the thickness of a dime would be considered “normal”. With such large gaps there are a couple of approaches I might use. You can use latex/water based fillers sold in tubs at flooring retailers, such as Bona or Woodwise filler. You could then fill the entire floor. Given the size of the gaps, you would have to do this several times. I would allow over night between filling. The one draw back with these fillers is they tend to pop out if there is movement in the floor. Another option is to use Timbermate wood filler which promises not to crack out, and this filler seems best used for large gaps only, since I have heard it is quite difficult to sand. Or you could squirt some moisture cure urethane adhesive into the gaps. This adhesive can be purchased from Home Depot. This will foam up as it cures but is sandable and stainable. It will never pop out. when it dries you could sand it flat and apply above wood fillers over top of it, just to fill in the air pockets that are exposed when you sand the surface of the adhesive.
Just a few ideas.