Super Slow WP Site and High CPU Usage - How to Fix and possible to redo everything from scratch?

Hi folks, need your guidance, I hope it's not too much of a trouble.

My site (David Simple Photography - Simple Flash Photography Tips, Beginner's Lessons, all Free! - non-IM related) has been experiencing CPU Throttling penalties for quite some time. To the point that bluehost shuts down my site once in a while as my site's server load is affecting the other sites, according to them.

One of the most obvious problems may be plug-ins, so I turned off and deleted quite a few of them and saw some improvements in terms of CPU Throttle stats the past few hours (used to be 800sec-4000sec per HOUR last night to this morning - note, I'm in Asia), then after I removed like 5-6 plugins, mostly social sharing, related post/linkwithin, ppinger, cloudflare, etc. The CPU Throttling report on BH dropped to between 300-800 sec. per hour.

The site's still quite slow according to Google Site Speed (new Analytics).

- Nissin Di622 Review page logged in 352.72 average load time (11 views)
- Flash Buying Guide is next at 151.31 average (3 page views)

The rest drops gradually from 80 to 8 sec rather quickly after those two pages.

Some site info:

- Hosted on Bluehost
- Latest WP install with a custom theme made by a friend
- Site is >2years old, about 100+ posts and articles.
- Current loaded/active plug-ins: All In One Webmaster, Amazon Localizer, cbnet Ping Optimizer, Dean's Permalinks Migration, Easy Privacy Policy, FeedBurner FeedSmith, Force gzip (newly installed this morning), Google Analyticator, Google XML Sitemap, Growmap Anti Spambot Plugin, IntenseDebate, JavaScript to Footer, Jetpack Lite, NextGEN Gallery, Onswipe, Pingler, Pretty Link Lite, SEO Ultimate, TinyMCE Advanced, TOC For Wordpress, Vibe SEO Pack, W3 Total Cache, WP-Optimize, WP tags to Technorati.
- Site average stats: 29K Visits/Mo, 24K Unique, 44K Pageviews, 2:16 Ave Visit.

My other sites (much smaller sites, some are niche sites) don't have a problem with load time, they pretty much load between 2-10sec depending on image load).
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My Questions

- Based on those info above (I know they're not much), can you pinpoint what the problems may be?
- If not, is it possible to start from scratch (clean WP install, clean DB, use a standard theme for test) without losing posts and comments? Will the problems just repeat itself when I restore the DB?
- If that's not possible or too complex, what's your best suggestion on tracing the root cause and how do I track site performance?

I apologize if my questions aren't that techy. I know very little about PHP and databases, but I do pick things up quickly if they're not too complex.

Hope you can help me out. Thanks.