Making crumb firmer

I'm new to baking and as such have been trying several of the recipes in Jim Lahey's "My Bread".  If I use the times and higher temperatures he suggests I end up with a bread with an overly hard crust.  At the risk of being too chatty, I outline my process for his Pane Integrale in an e-mail to a friend:

"Today I baked a 2# demi-whole wheat (25%) in the Dutch oven. I'm trying
to get prepped for Christmas and an additional 6-7 bread eaters in the
house. I'm using Stone Buhr bread flour, FWIW and ~78% hydration. Anyway I
mixed things together yesterday after lunch and by 8 that evening had to
stir the first rise down somewhat. Very perky! The next morning ~4 since
it was rising so well, I decided to move ahead with the next steps. I used
a much larger board that I heavily floured with a sugar shaker and eased the
dough onto it. Boy, putting a Tbsp of olive oil into the mix sure does make
the dough come out of the bowl cleanly - there was almost no cleanup.
Anyway, I floured the surface and patted it down and - perhaps because of
the heavy flouring - the dough was really well-behaved during the folding
process. I even needed to brush off extra flour from the surface and it
didn't care. Let it sit for 15 minutes covered with plastic wrap and then
into the parchment covered second rise container. At this point I dusted it
with corn meal and did the touch test several times to calibrate myself with
respect to how rapidly the dough sprang back. I then covered the dough with
a slightly moist cloth so that the skin would remain fairly soft and expand
easily. About two hours later, the dough seemed to spring back more slowly
so at that point I started to heat up the oven. I have the pizza stone on
the very lowest rack just to see how it's behaving and to add thermal mass
to the oven. The bread in the Dutch oven went on the rack in the next
position above the stone. I tried a single cut with a razor blade on the
surface of the bread. The cut was a little ragged because the dough dragged
somewhat when cut. I undercut the surface and made it ~ 1/4" deep. The
oven was at 450 F for the baking process so as not to scorch the wheat
bread, then dropped to 425 F when the lid was removed; the usual 30 minutes
for the first part and 20 or so for the second. The cut part of the top of
the upper surface looks really interesting. Perhaps it's the gluten
strings - the spring seemed to really open up the cut and stretch/tear the

fabric of the dough.  Anyway, the bottom came out not scorched, the crust is thin and pretty crunchy (but no singing during cooling) and the hole distribution in the crumb pretty uniform with a
few somewhat larger holes near the surface. "

The crumb is very springy but not very firm.  I stopped the baking when the crumb temperature was between 200 and 205 F.  So I wonder what can be done to make the crumb more firm?  Thanks in advance for whatever help anyone can offer.

  aloha,

Kawika, Hilo, Hawaii