Well I looked at your template site and to be honest with you the mark-up was less than desirable to start a Shopify project from. It is also a table based layout. I have to say in many instances it is sometimes easier to re-build a site from scratch than to try to adopt old code into a Shopify store, this is perhaps one of them. So statements like "significantly reduce development time" and "keep costs down" are rarely true and can scare off a potential developer. Unfortunately many, like myself, who do this for a living will look at that code to gauge a timeframe and use the existing code as a basis for the time involved for production.
That said, I think if you can get some of these code problems sorted and keep bumping your thread, hopefully someone will respond. I hope that helps you a bit.
This isn't shopify specific, but I have to say Jamie is right on.
Although it seems counter-intuitive, working with someone else's design is usually more work. These sorts of projects always seem to run long for little pay and nothing to add to your portfolio.
Your post was full of red flags for me.
It's hard to hire experts when your approach boils down to 'this should be easy/cheap, because I've already done so much work'. If it was easy you wouldn't need to hire an expert! :)
Not trying to be harsh here, but yeah. Any time I get a quote request where the potential client seems to be undervaluing the time/effort involved I've learned to stay away.
I've made exceptions from time to time, but my general rule is that I don't even take these kinds of jobs any more.