Wanted: Recommended Backup and best practices for small (10 user) exchange environment

I'm looking for some peer advice on exchange care and feeding best practices.  I've been a bit negligent in doing maintenance and backups for exchange, but I'm looking to mend my evil ways. :)

Server Environment:
Windows 2003 Server, dual core cpu, 4gb ram, 300GB+ HD, acts as file/print/exchange server.
4GB priv.edb and 9GB pub.edb, 10 users.
Windows 2000 DB server
Windows 2003 Web Server
Linux PBX (asterisk)
(other servers have adequate hard drive and cpu)
all servers run OS mirrored HDDs (raid 1)
Some cross server backup is in place (phone system config files are copied to another server nightly)

We currently use an offiste back up (ibackup) that runs nightly.  We are currently backing up 86GB with a daily churn of 1-3GB.  We also backup to a DVD set monthly.  DVDs cover our web server and important company data.  We do not backup our "job files" monthly (apprx 60GB of data).

I'd like to bring my Exchange data into my backup sets.  I can easily add it to the DVD routine.  However, I'd like to get it into a daily or weekly backup routine.  I've had a difficult time finding concise best practices that don't ramble on about every single option of every obscure utility that MS makes.  

Full daily backups seem simple enough, maybe to the DB or Web server to get away from a system failure.  However, I'm concerned that full backups would overload our bandwidth and "time slot" to upload data to our offsite backup.  I've considered Full on Friday and incremental a couple times a week to deal with this.  I try not to do offsite backups during business hours and during peak web hours.  This gives me a window from 11pm to 8am each night.  We have two lines a DSL and a T-1.

My current plan of attack is to develop a batch file that would:
- dismount stores
- ESEUtil with backup optioni to a specified place (in the backup tree)
- remount stores

Beyond that I'd also like recommendations on how frequently offline defragmentation should be done, and any other suggestions for maintenance to keep Exchange fat and happy and out of my hair.

About me:
I do have a fair amount of IT experience, but have been "in the weeds" since 2002 running my own small company.  Prior to that I was accustomed to large shop practices.  I did have a MCSE+i and a CNA at one time.... However, I'm humble enough to realize that I don't put out Exchange 2003 and Windows 2003 fires on a daily basis so I'm looking to learn from other people's experiences.  I want to create something that I can check on from time to time that will help me guard against equipment, facility, and stupidity failures.

Thanks for your help.