If you threaten something, always carry it through if he persists with the behaviour. Do not be surprised if he persists, just sigh and put the toy (or whatever)firmly out of his reach. Some children need this to happen a lot before they get the message that parents mean business. You say he really doesn't want to lose these things, but most children have a lot of toys and showing Mummy who's boss can often be a lot more fun.
If he's blowing raspberries when you put him in his room, that means you are still giving him your attention while you're trying to give him time out. Time out should mean being ignored by Mummy and every one for a short time (1 minute should be enough at that age) and then you say "why did you have to go to your room/the naughty step/the corner?" and don't let them out until they give the right answer.
There is no reason to expect calm behaviour at all times from a 5 year old, regardless of the personality traits of the parents. A child will test the boundaries and you just have to let them know what's acceptable, what isn't, and what the consequence will be
for continuing with certain behaviour after so many warnings.
On the other hand - pick your battles. It is exhausting to pick on every little thing. Also, I personally sometimes just pass the buck by saying to dh "Dh! He's said no to me" and he deals with it.
If you can see things escalating, you can try to distract him before it gets to the stage that you have to put your foot down.
Also: Catch Him Being Good. "Thank you for coming to bed calmly - would you like a story (or an extra story) tonight?"
Try to give him treats for good behaviour as well as pointing it out positively.