1. When i try to send someone coins, it says: Invalid to address: (walletaddress here to whom im sending.)
I tried Integrity check, I got this: Private key does not match bitcoin address
Which wallet are you using? Whats the bitcoin address you are trying to send to? You could check on a blockchain explorer such as
https://blockchain.info if the address is valid.
A bitcoin address often starts with 1, if it is a multisignature address it can start with something else. A Bitcoin address is an identifier of 26-35 alphanumeric characters, beginning with the number 1 or 3, that represents a possible destination for a Bitcoin payment. An example of a Bitcoin address is 3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy.
Bitcoin transactions are irreversible, so be careful to not send to the wrong address.