Thanks Dennis.
The links mostly pointed to our home page and some of our main category pages, so those did redirect accordingly. We also saw a slight decline in during the Google updates, but had recovered most of the way from those. In GA, it is easy to see the traffic drop begins when our redesign launched.
You said, "If you are sure that the technical issues are the main cause for your drops, then you better move it.". To be honest, that's what we can't figure out. Did the lack of comprehensive 301's which caused a lot of 404's cause this, or our platform choice. That's what we don't know but are trying to figure out before we make a big move.
Our product catalog is probably around 600+ products right now but will be heading into the thousands by year's end.
Don't know if this response helps at all or not.