I just made that exact recipe, and without squeezing out the wort at all and filtering out the hops at the end I ended up with just below 4 gallons. I started with a bit over 6 gallons, and usually lose a gallon to a 60 min boil+steep. So with the 90 minute boil, I'd guess I lost 5/4 gallons...
No, 33 IBUs is rather tame, although everyones tastes differ. What kinds of fermentables did you use? Usually I have that problem when I overdo adding sugar, and it ferments out too dry.