Not sure why you had 2 pieces of equipment 924 and 3000 to do fax the 924 can do 24 copper trunks.
Any way if you're going fiber internet why not just deliver as SIP and get rid of the 924 all together. Your new configuration is going to be internet to IDA (all the CLEC down here are using Adtran 924e Gen 3) to convert SIP to PRI then you are using your 924 to convert PRI to SIP.