Down syndrome & ASD newbie mum

My son is 19 and last year was diagnosed ASD. He has Down syndrome and the added diagnosis has been a huge lightbulb moment for me. It explains a lot but also leaves me feeling a huge failure. I’m trying to learn what I can and am totally overwhelmed. Right now my biggest worry is how to motivate him to do anything during this weird time. If he could, he would spend the whole day and night on his iPad or iPod either listening to music or watching YouTube (he has a need to watch highly emotive things like screaming fights on soaps or fans crying at concerts)

I find his stubbornness a real challenge and am constantly taking away his iPod or iPad in a fit of frustration to get him to do anything. 

I know I need to lower my expectations especially right now. But how do I balance making sure he’s getting some stimulation outside his devices and still learning something (eg trying to build his independence skills by cooking with me) with giving him the space and support he needs. 

I just feel I’m failing him on every level.

He has an older brother and younger sister and his dad at home too all self isolating together. His brother is exercising with him most days which is great. He does this happily as idolises his big brother. Should I use this as a reward maybe? But I don’t want to spoil their ‘thing’

my husbands great but totally leaves me to it and doesn’t seem to stress about how our son spends his time. 

Any advice or suggestions would be great.