With regards to Data's mortality, there has to be a limit, because in Descent, Data wanted to disable the safties so that there was a real element of danger. So yeah, on reflection, perhaps he's not all that immune to hand-to-hand combat.
That's not a very good piece of evidence, though... Computers in the 24th century are very likely able to customize holodeck settings based upon the individuals physical capabilities and limits... otherwise, just what would 'holodeck safeties' mean anyway? Worf's 'limit' would be quite different than, say Melora Pazlar.
In a way, this would apply even more to Data, since his specifications and hard limits are well documented and more defined than organic beings. There are no established limits on holographic strength, so it's possible, theoretically that the Doctor (EMH) could beat Data in a test of strength.