Unfortunately, this is not possible. The link is done on the SuperCell servers, and there's no way to unlink an account from a Google+ (Android) or Game Center account (iOS).
You will need to create a new Google+ account to link to your village.
Just FYI, there's some information I found on Google that suggests you can unlink it by going into Google+ settings. I just tried these suggestions with a test village of mine and can co firm that process doesn't work.
Mass Dragons + Rage Spells is one of the most effective strategies for getting stars around TH7/8, in my opinion. It's generally pretty easy to deploy as well.
That said, as you've noted it's very resource intensive. The thing is, Clan Wars aren't really great for elixir gains. You're much better off with collector raids with BARCH to get elixir, and even gold for that matter. Clan Wars are really mostly good for getting the Dark Elixir bonuses.
There are a couple of alternative strategies, though, that you might consider.
One is Giant/Healer which is basically just a swarm of Giants, with a few Wall Breakers to speed up the process, and 1 or 2 Healers and Heal spells to back them up. The problem with this is speed - Giants are slow. You might have the base dead to rights and run out of time - especially when factoring in the time it takes to lure the Clan Castle. Also the Healers are air and the Giants won't tank air defenses for them.
Another is Dragons + Balloons. Balloons are somewhat cheaper and they target defenses. The Dragons can drop first and tank for the Balloons, which makes them a bit more likely to hit air defenses before they get taken out. This strategy works best when the AD's are close to the outside of the base, and you can blitz them quickly.
DE troops at TH7 are both weak and costly, so I don't suggest using them.
Another important factor to consider when choosing a war raid troop composition is what troops and spells have you upgraded? Ideally you want to max out your troops before you use them in clan wars. Even with the best strategy and perfect troop mix, if your troops are underleveled the attack will go to waste.
Best Answer
When you disconnect the attack keeps going on the server with the troops you deployed.
In your case, they are able to destroy the townhall which results in one star. After that, the attack keeps going on the server. When the attack ends, because the time ran out or all troops have been killed you are awarded with the loot, the league bonus (if you got at least one star) and the trophies.