Just a couple humble opinions from an agent here in Oregon...
The supply of entry level housing is very low, keep in mind that trying to get an offer with any kind of a rehab financing accepted in this market is tough - so I'm not sure I'd be so quick to throw your REA under the bus just because your offers were rejected.
With that said, you are correct that it's your REA's job to understand how your rehab financing works and to find a way to make the seller comfortable with it. Most sellers (and their agents) are uneasy with rehab financing for no other reason than they are unfamiliar.
More important than your agent's experience with any specific type of loan program - you really need to sit down with a lender who has sufficient experience writing this kind of loan. Ask how many rehab loans they've written this year when you call to set up an appointment - if their answer is less than 5, call someone else. Once you find an experienced lender you are comfortable with, get a pre-approval letter and get the loan program details to your REA. A good lender will be happy and available to work with your agent to explain the ins and outs of the loan program and differences in timelines, inspections, and appraisal that typically come with a rehab loan.
Prepare yourself and your patience for what could be a lengthy process. I have buyer clients right now that are pre-approved for 203b/203k loans and have made offers on 15 houses in the last 12 months. You might also consider private money, a seller carried note, or expanding your search area a bit out of Salem proper - those are a few things off the top of my head that might get you into your first home a little quicker.