As you say, the work can extend over periods of time, but this is just a reflection of the deep release of lifetimes of negativity. You appear to have come across an energetic holding that was previously not apparent. So, that's good - you're continuing to make progress. There's no reason to become discouraged, just keep on with the work. I hope you've read Deep Clearing carefully, since it goes into more detail than the previous book.
Also important to never forget is that our personal subconscious Karma determines the childhood we are exposed to. It's vital to drop blame.
What you are describing (block of energy that was stuck in my chest) is typical of what my clients report. We just apply processing techniques to the block and it starts to unravel.
I was somewhat dismayed by the title of your post - struggling, but then you explained further about calming. EC work is never about struggling, it's about acceptance. It's to relax deeply into the alpha state, and just be present non-judgmentally with whatever is there.
If you're asking about other complimentary modalities, sure, other approaches can augment EC work, but they should be right-brain, energetic, such as chakra clearing. Body work such as non-power yoga can help loosen up energetic congestion. It's not a bad idea to do a few sessions with an EC Facilitator.