I am pleased to say that compensation amounts for injury to feelings is well outside the range of my experience, something I have no intention of changing.
But it does seem to be about how 'bad' the incident is. So years of sexual harassment might be at the top end of the scale, but most aren't that bad and don't attract that level of compensation. So whether you'd be likely to get 6 months/a year salary depends on how much you are paid, and in your case, probably nowhere near, without obviously knowing the details of the discrimination.
I misread your post initially, and assumed the dismissal (in your view) for taking parental leave was for requesting it, and I was assuming that request was denied, and you did mention a request for parental leave later on. But if you took it, and it was because your son was ill, it sounds more like emergency dependents' leave, would that be right? That's still a statutory right you get from day one as well though.
It does all sound very involved and a bit messy - you say you've got sex discrimination, denial of parental/emergency dependents' leave and alleged gross misconduct in a very short space of time.
Legal costs are often something that is considered when a settlement is being discussed, purely because obviously the first thing an employee is going to need to persuade him/her not to take it further is not to be out of pocket, and this would involve legal costs incurred thus far.
It does sound as though you are on your way to possibly settling it, from the quick response you had to your most recent communication with them stating your intentions to file a tribunal claim and registering your appeal as part of the grievance process. I hope that's the case. I would probably be advising the organisation to settle it as it sounds messy, time consuming and potentially embarassing. If you get an offer your solicitor will obviously be able to talk you through what realistically you could get in the event of a tribunal, balanced against how much that would cost you financially and emotionally to bring the case.