Oh no you must be exhausted.
Do they go to Nursery or a Preschool? If so any concerns about behaviour there?
Have you spoken to your Health Visitor? Online Twins group?
Easy to say but I wouldn’t shout or threaten. Three year olds soon learn when so called threats aren’t carried out.
Try to ignore negative and praise positive behaviour if you can. Maybe make some rules together, represent visually
If throwing reinforce with a visual saying Throwing toys, toys have finished ( put up high or lock away)
Have you tried reward charts, are they competitive at all? Catch them being good
Good sitting, eating, playing etc for a sticker token etc
Set some challenges for tidying etc using a timer or first one to get ten things in a box for e.g.
I wouldn’t beat youself up about tv or ipad time for calmer time for you. Timer if they are sharing something.
Do you have outdoor space? Lots of free activities and resources out there painting with water, chalking, making dens etc.
Anyone nearby who can help out to give you a break or maybe separate them for a while?
Sure I’m not saying anything you don’t know but sounds like you need some help and a break.