You are making a Rod for your own Back by attempting to do this as what's going to happen the next time that the Password becomes corrupt or it gets changes without someone notifying you?
What you have to remember is that while it may be easy for you to drop in a Live Linux CD and Boot from that and then change Passwords this is something that the average end user can not do so it really isn't a problem.
But if you want you can leave the Floppy in Place and set BIOS to boot off the HDD ONLY so that will bypass the Boot From Floppy and Optical options you just have the one option in BIOS to boot from the HDD as a first option and all the other options disabled.
As for making it impossible to have physical access to the chassis you can always seal them with a locking device of some description. Most new chassis have a sealing tab sticking out the back that you can put a locking device through to prevent tampering.
For 5 & 6 this is done at the Server and is a standard setup for any Windows Domain.
7 is the hardest one I once filled in the power plug with [b]Epoxy Glue[/b] to suit a customers request for a [b]Totally Secure Workstation[/b] but of course while it looked nice it was unusable.
Yes you have gone way OVERBOARD here the Live Linux are a great Tech Tool that are indispensable to every tech but honestly I've yet to find any end user capable of actually finding an ISO of one to download let alone knowing how to use it once they have it given to them from a Disc Cover on a Mag or something similar.
The main risks that you will encounter is that when something does go wrong you will have effectively locked yourself out of the system and it will be time consuming to get back in to correct the problems.
By the way Windows and Security should never be used in the same sentence unless you expect any decent Tech to fall to the floor laughing. :D
Col