Hi Kid C.,
I think your scans look good overall and as far as I'm concerned they are surely good enough to be posted. I personally think they could do with a bit more colour,but that may be a matter of taste. I would prefer 150dpi scans, but more is indeed not necessary.
File size itself of course depends on the size of the mag, the resolution and the JPEG compression. I think you can compress your scans a lot more and save file size and upload/download time. here's one I reduced to 30% of the original file size:
I used Irfanview at the 80% quality setting. Can you see the difference?
Another suggestion: use Imagebam or Imagevenue instead of P&H.
Happy scanning!