My nearly four yo sounds very similar.
She's very 'emotional' about lots of stuff....a drama queen really. Gets hurt at the slightest thing. Funny though her teachers put it down to her not having older siblings - she just wasn't used to it. They never said it was wrong
Similary she's been through a signing phase recently. I think it's just them figuring out that communication doesn't have to be via speaking alone - just a new discovery from inquisitive little minds (well as annoying as it was that's what I kept telling myself).
She also does oddly unsocial things and says weird things....just testing the (my lol) boundaries I reckon. No-one actually tells them what they 'can' say so they're figuring out how it all goes together.
As for the scissors and the mirror writing. DD and I are both very left handed. My mum was a leftie too and so that's the only way I've been taught. Scissors hurt when you are a leftie...they feel weird, they aren't made to be used in the left hand. Fiskars make some great kids spring scissors without the finger loops. I have a pair and I'm trying to find DD some - makes life much easier. I can also mirror write at the drop of a hat - and I've been writing for years. DD often copies letter I write in reverse. I'm not dislexic. They don't understand the rules of left to right, top to bottom straight away. To them, the letters are still just shapes.

He sounds like a great imaginitive little guy hun.