Change in job responsibilities, but not pay

[NettlesAreEvil]

I have worked for several years in the same job.
6 months ago, my colleague died at work. It was an extremely traumatic experience as I was alone with him at the time.
Despite the flashbacks and nightmares, I did not take any time off work, and continued working in the same room, which I found very difficult.
Another consequence of his death has been that my job description and responsibilities have changed and increased significantly over the last 6 months, as I am now covering much of what my colleague used to do.
However, my salary has not changed and I am still earning half, if that, of what my colleague was.
I have asked about this on several occasions, but after initial promises that my salary would be increased to cover the change in my job, it does not look like this is going to happen, beyond the nominal annual inflation increase.
It this just a case of if I do not like the situation, I should either accept it or move on?

Oh poor you, that must have been awful to experience. But you are being taken advantage of. Tell your boss how your responsibilities have increased and ask for a pay rise. I bet they would really struggle without you. If none is forthcoming look for a job elsewhere.

What a horrible experience :-( I'm so sorry to hear that :-(

They have scored here because they're no longer paying your previous colleague and haven't adjusted your wage appropriately?! Good to be them I say!

Ask again for more money, be honest and say that you will look elsewhere for work if they don't take this seriously.

So, I discussed the possibility of a pay rise with my boss, on two counts, that I had worked there for two years and was due an annual increase, and also the very changed job responsibilities.

I was told that I would definitely get a 2% annual increase, as is standard across the company.
I have now heard that yes, I would be getting an increase above this to reflect my changed responsibilities, of approximately 10%.
However, it turns out that this also involved me increasing my hours, which I am very unhappy about. I am a single parent, had a total career change to be able to work around child care. As it is, he spends an hour in after school club every day and I work evenings to make up my hours.

Currently I am supposed to work 9-5 (or equivalent) with 1 hour for lunch, but I generally work through most of this due to the extra pressure after my colleague died.
The salary increase is dependent on me halving my lunch break to half an hour a day.

So, if I calculate this, if I stayed in my previous role, increased my hours in line with the above and factored in the 2% standard increase, (which I haven't actually had yet), the new role salary increase amounts to less than £700 a year, which feels like quite an insult.
My boss says I should just agree to the hour change as I generally work the extra anyway, but that he wouldn't expect me to actually increase my hours. I am really not happy to do this. If I have to sign a contract to say I work longer hours, then I will work the extra hours. We work for a much larger organisation.

Any suggestions. I am really not looking forward to discussing this again tomorrow. It is just the two of us in the office and I think he is losing patience with me over this already.