Hi Wayne,
Firstly I would look back at what the scope of the project was, what were the aims and objectives of the project? This should help you answer whether or not you have been successful in achieving those goals. Let me first address some of your concerns on the drop in links etc:
Domain Authority: 29 now 28
Domain Moz Rank: 3.30 now 3.98
Domain Moz Trust: 3.47 now 3.76
Total Links: 3,053 now 6,123
Ext. Followed Links: 2,995 now 378 (hoping someone might be able to explain this also!)
Linking Root Domains: 21 now 28
Followed Linking Root Domains: 18 now 26
Linking C Blocks: 16 now 22
SEOmoz have made some updates to the crawling - sadly, with a few hiccups. The new crawler is built to be fresher, but it is going deeper into domains, and, unfortunately, not visiting as many domains. Domains with a high MozRank are getting crawled deeper, but domains with middle to lower MozRanks are not getting crawled. Their top priority now is to get the domain diversity back up to or better than that of our last update (as was originally designed) so that they should have many more inbound links.
The above can be your answer to any questions regarding the drop in stats, explain that it's not that anything has been done badly, it's just the way it's being measured and should return to normal after the next update (hopefully).
If you have been building links you should also have a list of domains that you can prove you have been building links so again I wouldn't worry about explaining that.
Some good ways to measure success other than ranks are:
-Traffic volumes
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Number of referring domains
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Number of referring keywords
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Average time spent on site
-Reduced bounce rate
Some of those might not be relevant if all you have been doing is link building but take what you need and leave the rest. I think the best is to look at traffic and number of keywords referring traffic. The reason being, while you might not be position1 or on page 1 for a lot of terms yet, you may be getting a lot of longer tail traffic which you can definitely take credit for.
I hope this helps
Craig