I haven't read the whole thread, only got to about page 5, but here are my thoughts on the subject....
Are You Being Unreasonable? Yes. Although you have suffered difficulties in life and put a lot more into the "system" than you take out of it, you are actually in a very fortunate position compared to a lot (most) of society. I am sure it may not feel like that on a day to day basis, but when there are people who cannot provide food or warmth for their children then complaining about such a high tax bill is unreasonable.
It seems that there are other factors which drove you to "crying point" over your tax. What stands out to me about these is that YOU CAN CHANGE THEM. For example you could work less hours, you could start claiming invalid benefits for your husband etc. That other people are in situations that they cannot change is why you faced such vitriol in the responses. Because people think "oh dear, poor her, in a situation of her own making that she can change and she wants us to feel sorry for her".
All that said, I do understand that you are taxed a lot - as am I. But I do not begrudge it. Having spent a lot of time travelling in developing countries I really appreciate what my taxes provide in this country (even if I moan about the NHS too). What they fundamentally provide is a safe country - where we are not subject to high levels of crime just because people need to take from others for their basic survival and are driven to violent uprisings to protest about their situation. When I look at colleagues who live in Kenya, I realise that although they pay less tax, they end up spending that money on private security instead.
Maybe you should use this crunch point to re-evaluate things in your life and decide if you are truly happy and if there is anything you want to change. Because you are lucky enough that you can.