How likely am I to find blocks mining solo w/ 450kh/s?
You can look at a pool (or one of those calculating websites) and look for someone with a similar hashrate (or type in your hashrate). By the nature of crypto, you should ideally earn the same number of coins regardless of how you mine them, so if you would get 64 coins per day, that's 2 blocks per day.
Hope that helps. You should get over a block a day.