I agree with your point on the OL, and I was a bit optimistic on the matchup with PSU going into the season actually. I thought our D this year was better equipped to defend a lateral spread-style offense of theirs than a downhill running attack of Wisconsin (I was particularly worried about our DEs in this regard, though they held up respect, at least for a half). Two things make me more worried now though- 1) the erosion of our CB depth, which will cause problems (partly in guarding Hamilton et al, but maybe even more on run support and open field tackling of Barkley); 2) without naming specific names, I have been somewhat less impressed with 1-2 of our LBs tackling abilities this year than I had hoped, which could pose a problem.
Fitz and Hank though I expect will be drilling on how best to contain and tackle Barkley all week long. Like with past otherworldly RB talents (M Gordon for one) I suspect he'll get his yards, but I also suspect we will come up with a game plan to prevent him from completely taking over the game like he did against Iowa and Indiana.
On other weaknesses for PSU - their D is a fairly decent step below Wisconsin's IMO. It's good, don't get me wrong, but I have more confidence in our ability to put up points against them. If we don't turn the ball over, I think we can very realistically score 24+. It won't be easy, and I don't expect a win by any means, but I think a spread of ~10 is more fair than the -14.5 that is showing currently (funny, I said the same thing about last week...)