Since nobody answered yet, I share some thoughts regarding your questions
I had an idea to solve it: to hire someone inside China to do such stuff for a reasonable fee. like sending him the boards from pcb manufacturer and assembler, then he does the programming or putting the product together...etc. then he does testing with provided test rig or so... THEN he ships the products to nextsmartship to be 100% ready to be shipped.
Have you considered 7-day trip to China? Two-way flight ticket + 7 days x 400 CNY hotel + other expenses. It may be cheaper than "reasonable fee".
I think, it's even possible to order something and receive in a less than a week using SF Express, shipped to your hotel address. Or negotiate with fulfillment company if you can visit their storage and get your product ready for the client.
Idea 2 - Learn how to work with customs in Jordan, you have a potential to solve it. Consider different point of view, where problem is in your product and not in custom fees. In other words, your product may be not profitable enough.
Idea 3 - Try to minimize number of operations and entities involved. E.g., maybe fulfilment company is able to do some of this testing. Why it should be a different person? Explain operations needs to be made in simple terms, something like "need to plug each device X in USB port and press a button on notebook program Y" and provide a simple photo. Sometimes very smart people got scared away by something they never learnt, you can avoid this by pretending operation is simple, and making it simple too of course.
1- what if I need to test the products before considering them ready? like if there are some faulty units. I assume pcbway or the likes of it can do some testing if provided with instructions??
For 100pcs product, providing instant refund for failed unit is probably cheaper (no return needed, just give people their money back). Try to put more effort in making it more reliable from manufacturing point of view. Maybe only consider this if something starting to sell very well and you need to optimize your process before you run out of stock.
2- what if the product needs MCU programming or similar manual preparation. I see Digikey offer programming feature which can be used but also one should guarantee the pcb house to be able to do it. please state your experience in this. also, if I want them to insert the board in enclosure and tighten it...etc.
Probably too expensive, and SMT assembly company needs to get your chip from Digikey(?). I'm not sure what kind of MCU you are using, on STMs you can flash chips using internal bootloader, this operation may be combined with testing person from your first "1-" question. You can even make a small USB-powered flasher device with two LEDS: red - power/not flashed , green - device already flashed. Some person plugs it in dedicated port of your product and waits LED to become green.
You may consider shipping unassembled product, e.g. a DIY kit: well packed enclosure, screws and PCB.