I have Brocade Silk Warm 3900, 3800 and 3850 switches. I have following issue with these switches.
2. Obtain them though your vendor/reseller or have a active brocade contract, with th elatter you can access them on the MyBrocade downloads section
3. define slow....all but the 3850 are 2Gb switches so initiators and targets capabel of higher speeds will be limited to 2Gb, the 3850 is 4Gb so same applies for device capable of +4Gb speeds. AFAIK all switche are nonblocking.
With the issues you have combined with age I suggest you replace your current set with new ones, 6505 or 6510's will do the job unless you have 1Gb devices.