At the very real risk of having my face set on fire because i am a/ not a parent of a toddler and b/ going to apply dog behaviour modification methods...
He is frustrated, he cannot communicate clearly, he lacks the motorskills to achieve the goals he is trying to achieve or the ability to explain what the problem is.
He is attention seeking because he feels the need to do that - so for him, that need is REAL even if you don't think it is.
You are failing to resolve the situation because all of your efforts are geared towards stopping the behaviour you do not like, punishing the behaviour you do not like...
You should be looking at finding out WHY the behaviour happens, offering appropriate outlets for behaviours, finding out how to avoid certain behaviours.... and THEN your methods like time outs MIGHT have a useful effect.
Time outs btw are ONLY useful when you have addressed all the other aspects, otherwise all they will do is build frustration and since the problem behaviours are almost all to do with attention and frustration thats definitely going to make matters worse.
Time outs are also only effective when they are crystal clear, consistent and fast - most peoples time outs are fuzzy, long winded, not clear as to what behaviour triggered them and not remotely consistent and again this will ramp up the frustration!
If he is throwing toys after trying to play and failing to achieve his goal, are the toys actually suitable for him?
Can you help him? Encourage him to talk about what he is struggling with and how you could help?
Can you redirect him into a more achievable form of play with that toy, or with a different toy?
The more frustrated he gets the more he actually needs your attention but will be unable to ask for it nicely, and the less able he will be to tolerate having to wait.