Hello Starlight, I understand what you say about grieving for the life that could have been. You are happy now as a SAHM, but you know it is not a long term solution to be out of work. And you like the work you do now. You don't want to be forced by silly childcare costs and financial circumstances to give it up forever for a lowly paid term time job.
It is really unfair to force your hand like this.
You are at a turning point, in that you are nearing the end of your second maternity leave. You have been too busy with your baby to think through your options career-wise.
Taking a sabbatical or career break re; your employer is a good idea and one I know you are pursuing. On another more informal basis, you could also try networking. I know I am poor at this, but it is really simple like keeping in touch with your colleagues and counterparts in your old job. So that when a position comes up in the future, they have you in mind.
If you want a flexible job, they don't tend to be advertised and you need little inroads like this to get them.
To do that, you need to carve out a slice of time for your self, like using free nursery places once your dd is 3 and reciprocal arrangements for your baby like itistooearly describes. And keep updating your CV, reading in your field, like you are doing.
I think a break from your work, that is not completely dominated by childcare/housework, can broaden your thinking laterally.
Who knows, it might take your career in a new direction once you have the time to research and ruminate.
Try to stay positive and reasonably focused. I am sure something will come up in time when you are ready