Going 50/50 on SPY/TLT won't help. SPY puts are expensive. Stop loss orders cause $$$ loss due to head-fakes and flash crashes that recover quickly. Selling covered calls doesn't bring much protection. What are some other ideas?
Cheap OTM puts should work. Maturity can/should be longer than your calls, if applicable, for example by 1 month. Of what investment amounts do we talk here?
Index hedging is very expensive. Best hedge is reduced position size. There's still an opportunity cost but it's only relative at least.
Can you give an example where it would be expensive? IMO any options price is fair due to the Put/Call parity, and you can very well use it for hedging, after all they are made especially for this scenario. You don't need to keep it until maturity, just for the timeframe where you need the hedge, and then simply close the hedge. If it is still somehow subjectively "expensive" then just use the "cheaper" Out-Of-The-Money strikes. Isn't it?
when comparing costs, don't forget to calculate in the cost of cap gains if you sell instead of hedge
Put-call parity doesn't imply that the prices are fair in any sense, just that puts and calls are equally fairly (unfairly) priced. The market may still over or underestimate volatility of the underlying asset.
You said that hedging would be expensive for indices, I questioned this and asked for an example, but you neglected to give an example. Since puts and calls are equally fairly (or let's assume unfairly) priced, then it doesn't make any difference for hedging (or whatsoever), because when closing this options position then any inequality turns into a net equality, due to, as said, the Put/Call parity.