1) When the Inspector comes by, he's going to see that you didn't follow the plans, and he'll require you to talk to the Engineer anyways. 2) I, personally, don't know how to calculate the load, and don't think it's prudent to do any of this type of work W/O the help of someone who 'knows what they're doing AND can see what's going on. (The WEB makes it difficult to do very much.) 3) IF you don't follow the advice of the Engineer or don't see his advice in light of your changes, the 2nd floor MAY end up on the 1st floor, and it will be impossible to explain to the Insurance Adjuster why the 2nd floor is on the 1st floor.
I know this isn't the answer you're looking for, but in light of the circumstances, your BEST served by paying the Engineer to re-do the work. I can't imagine that he'll charge that much given he ALREADY has the load information, no? I mean, I can't see him charging you for more than an hour's work. It's a recalculation. Plans don't need to be drawn up or anything. I may not be understanding exactly what you're trying to do (because, you know, the WEB is 'in our way), but that's how I see it. I wish I had a better answer.
Yes, you could take your chances, but again, the Inspector may nix the whole thing and you're stuck w/having to ctc the Engineer anyways. Avoid that 'mess' and any further delay by going directly to the Engineer. Maybe you can ask your folks (and children if they're off and working) for an early Christmas / Hanukkah present. The cash would pay the Engineer's fee.