I think... you have all this backwards actually.
1) I'm not terribly sure where you got the idea that we're responsible for the tension between Ukraine and Russia? That stuff started way back in 1920 after WW1 and the more modern stuff, in 2014 from Putin. It was the Russian Federal Assembly which voted to allow Putin to "invade" in 2014. Putin is way too smart to let a dumb country like our's interfre with something that has been going on for like, nearly 100 years now.
2) Also not sure with what you mean by "They don't allocate their resources correctly" as this seems like a weird thing to say based on your examples, literally every country does this?
3) It wouldn't be great for us to leave, and about half the country, "officially", doesn't want to leave. The other half where fed total lies and broken promises.
If we leave the EU, we will lose access to all the free support and constant grants that they give us. This will hit almost every single industry in a very negative way. This will then pass on to effect all trades and such in a very bad way. It's a domino effect, except when the dominos fall, that's one more broken promise and one more thing that has messed up.
If we end up leaving with no deal somehow, we likely will end up with some catastrophic results which would kill our economy much more. Getting out of the EU is the worst choice, that again, no one in parliament ever actually wanted. Cameron did the vote as a last-ditch attempt to get re-elected. If you notice, he ran with his tail between his legs when he realised he lost and left the country to die. He's very much hated atm.