Not quite it with the going further by 20% a day mush. Starting slow really means starting slow. So do the 20 and the 5 tomorrow, and the next day, and the next. When it doesn't feel like you're going to die and you think you can squeeze another 2 out, do them, but otherwise you'll just hurt
A really good exercise plan for at home is the British Army Circuit training for pre entry exercise. It sounds scary and it won't be for beginners initially but google it and take bits from it to use. It's made for being used at home with no equipment so when you can start doing the different bits you could start using parts you like and work your way to being able to do all of it.
That and you're saying running isn't for you, how about trying swimming? It's low impact as you're being supported entirely by the water and you can go at your own pace, even if you're just floating around at first. Even 15 minutes a day of splashing around is a great start.
And yeah it's not about stopping eating, it's about eating the right things. Veg is good, pasta is healthy. Fruit for snacks etc.