I have a couple of questions about setting up an RS485 network with multiple 16f88's to read DS1990a serial ibuttons.(Lock project for 5 doors)

As I understand the RS485 network I can have 32 nodes. The PC being the master and up to 31 16f88's as slaves.
No slave can initiate communication to the master(pc).
Each device has an address of 0 - 5 (The pc being 0 and all slaves are 1 - 5


What I am planning to do:

PC as the master
16f88's as slaves each has an ibutton reader attached to read serial number from DS1990a
Each 16f88 has a variable as ID VAR BYTE[8]
Each byte is set to all 0's
If an ibutton is read by a slave the 8 byte serial number is stored in id.
The PC poles (sends the address) to each slave and waits for a response, if the 8 bytes are all zeros the slave sends to the pc "255" for no data to send and the pc moves on to the next slave.
If a serial number has been read by a slave then once that slave is polled "254" is sent to the pc indicating data will be sent and then the id is sent.
Once the id has been sent the pc compares it to the serial numbers in my database. If a match is found "254" is sent to the slave, the lock is opened and each id byte is set to "0", "255" is sent back to the pc to tell it to move on to the next slave.
If no match is found "255" is sent to the slave the lock is not opened and all bytes are set to "0". The slave sends back "255" to tell the pc to move on.

Questions:
1) Am I completely off base hear, if so could someone provide an overview as I have attempted to do above. I'm not looking for code just an understanding how I need to go about this.
2)Once a slave sends "254" to the pc indicating data will be send. Do I need the pc to signal the slave to send the data or can data be sent after the "254"?
3)For the sake of understand how fast all of this can happen, if I have 31 slaves on the network how long will it take for a complete cycle of the loop to occur? The pc is dedicated to this project and will not be busy doing anything else.

Thanks in advance for any assistance
William