I am afraid that, by cutting back and saving £100 (ish) per month, you have demonstrated that the allowances you were initially granted were too generous and that you can live on less ! I would use the arguement that some of these 'savings' are, in fact the sum of those monthly allowances that contribute to the bigger picture --- for instance, some of us are allowed, say, £50 per month car maintenance .... now, obviously we do not service a car a bit a month ! We save those £50, until they become £150, then service the car, or save them for that day the gearbox blows up ! Petrol money --- during Covid your mileage would have decreased, but it could go back to normal any time! I used to have £10 per month for entertainment ... so I saved this up until I had enough for a camping pitch for a week.
Take these arguements to your IP and, if no joy, make a formal, written complaint to them ( recorded delivery and keep copies ), which you can escalate to their regulatory body if needs be, via the Government Gateway. They are putting you under undue and unfair pressure as well as putting the arrangement in jeopardy by cutting things too close.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014