It is impossible to predict what schemes may or may not be available in 2 years time when you hope to do the course. As you correctly said, you won't be eligible for Back to Education Allowance.
If the course includes paid work placement, then the earnings may affect whatever Welfare Payment you're on at the time.
If you are on Jobseeker's Allowance when you start the course, going into full-time education would disqualify you from JSA under the current rules, as you would not be considered available for full-time work.
The reduction in the age limit for claiming one parent family payment will be phased in for existing claimants, so it may be some time before you are no longer eligible.