Not very smart of you.
1. You can be tricked into believing a transaction has been confirmed when it is not.
2. You leak information about which addresses belongs to you to full nodes you are talking to.
Well it is much less of a problem then getting hacked and loss all your coins on core. And you can't use it without a computer. Unless you use TeamViwer and get hacked that way... It must have some backdore since even with 2FA someone connected to it and downloaded wallet.dat for 2 times. So I really don't see how you can use core in any practical way...
LOL! Do you use Wintendo or some other virus hive? Don't use your toys for storing money. I run bitcoind on a Linux computer, which I can access over ssh from anywhere.
Any node can make up its of mind about what spam is, and have the right to decide it. There are some default filters, and some of them can even be adjusted by command line options. If you don't like it, use a bank. If you use an SPV wallet, the random full node it talks to will decide for you if the transaction you are about to send, or one you expect to receive, is spam or not. Users won't know what the policy of an individual full node is. The average policy of the network will be estimated by full nodes, and translated into fee and priority estimates. If you run a full node, you will know what is required to get a transaction confirmed with good probability within a given number of blocks. If you send from an SPV wallet, you must trust the defaults and the full node you are talking to.
If you don't understand why the idea any node can make up its mined is dangers I can't help you. Normal user will think that if something works one day it will work the next.
This is by design from the beginning. If you don't like the way bitcoin is designed, you should use something else. There is no way to change it. There is no way to force anyone running a full node to mine or relay any specific transaction.