Beautiful car there, Carlos! I'm sorry that you're experiencing issues with it.
There's a lot more to it than just dropping a Subaru engine into a Speedster. The largest issue with the Subaru conversion is cooling the engine. These cars were not designed to locate and effectively manage a water-based cooling system so whomever does the conversion has to know what they're doing. Beck (Special Edition) in Indiana have it figured out. From what we've seen/read on here, JPS (John Steele) seems to have it figured out, too, to some degree.
By the time you're done doing a Subaru conversion on a Speedster it will cost somewhere between $8K and $10K+ and the build leadtime right now looks to be around two to three years.
Alternatively, you might ask around in your area for another experienced VW shop so you'll have two quote/data points from people who could work on your car. Find a local aircooled VW club, attend one of their events and ask around for competent shops.
Most of the shops around me (central Massachusetts ) have technicians who not only have never seen an aircooled VW, they weren't even born when the last of the VW Beetles hit the streets! I just recently discovered another shop nearby that is a bunch of kids who adore VW Buses and learned on those and have made a business out of fixing them, along with Beetles. I've also lost two shops last year to guys just retiring. The knowledge base is shrinking by the month.