My advice would be to speak to your PPU officer...and a solicitor.
I know this isn't going to help but speaking from my own experience, any time i've disclosed i've either been refused employment or got fired. I've been lucky to manage to get work that doesn't involve any computers and is actually in a dangerous environment (construction) and PPU and my probation officers (when i was on probation) were happy with that, but it wasn't always like that.
It is going to be more difficult to maintain a job role where access to a computer and the internet is part of the job, irrespective of the IT safeguards in place by the company. But that all depends on the powers that be.
When i was dealing with probation, initially i was advised to disclose at every opportunity (even when not asked about unspent convictions) all that ended up doing was nurture a deep seated feeling of apathy and yes my mental health suffered as well, these were all low key blue collar jobs not public facing and no real risk of any children being present.
It was an awful time, giving out my home address and contact details to people i didn't know whilst disclosing my offense.
I've always found it very difficult when you are faced with someone new , be it PPU officer or probation officer, because you have to basically start back from square 1 again, going over your life story etc. Personally i have been very lucky with my probation officers and they have all wanted to see me progress, but it still makes it difficult when you have to build up a relationship again.
I wonder if maybe you could consider becoming a private accountant? it is a profession like mine in some ways where you could work for a big company or be self employed, at least if you work for yourself you can't fire yourself!
Today, being able to work is absolutely vital to keeping me in a stable and positive mindset, i think if you work in a very low to zero risk environment with regards to the nature of our kind of offense then i think probation can do more harm than good when they decide to take a moral stance which could cost the individual the very thing that is giving them stability and is a vital part of the foundation of living an offense free life. I think sometimes by trying to reduce or eliminate their perceived risks, they can be counter productive and actually cause more risk further down the line, if the loss of employment will lead to a poorer mental state and potentially bad coping strategies again.
If you said 'they want to disclose to my employer who is a toy shop' or 'my employer is a holiday park where families take their kids' then i would agree with a decision to disclose, but i think most people with our kind of offense wouldn't be so stupid as to even entertain the idea of going for that kind of employment unless they were severely entrenched. I think your probation officers perceived risk is solely the access you have to computers and the internet, my argument would be we live in the 21st century where everything is connected and the internet is now very much a part of daily life, a necessity even so whether you are at work or not, being able to access the internet is not difficult
I'm no expert but i think risk is always down to the individuals mind set, irrespective of external/physical things. I think if an individual was hell bent on committing another offense they would find a way, hopefully you want to live the rest of your life offense free and i think when a person has genuinely made that promise to themselves, nothing anyone can do will make you go back to making those bad choices.