1.)I checked the electrum code and it also uses RNG that just picks a random number between 1 and 2^256 so therotically RNG can a pick a 10 digit number too? or am i missing something here?
That's true only in theory. The probability of getting a 10 digit number is almost zero.
2.) Second question i have is. We all know how SHA256 can be used to convert any 'text' to a hash which is a valid private key right a.k.a brain wallets.
It's not recommended to use brain wallets. It's recommended that the private key is generated randomly.
So my question is what if my wallet generate a key which is secure but what if that key is SHA256 hash of some 'poor dictionary word'? There's no way to check this except comparing with all SHA256 of dictionary words. It's indeed a risk right? Am i being paranoid here?
No. There is no risk. What you worry about can happen only in theory.
A randomly generated private key is very very unlikely to be a hash of a simple word.