In general, though, by far the best option is just plain PayPal without intermediaries. The less friction you have, the more money you will collect. The thing about PayPal is most people already have accounts. Signing up for something else is friction. Providing financial information to a foreign web site is a complete non-starter. International SWIFT requires a trip to the bank, and a substantial fee, so it won't work either.
Also, I think it's a mistake to not offer commercial support contracts. Basically here's how you could "freemium" this: offer no SLA for non-paying users, offer guaranteed turnaround to paying customers (don't be overly aggressive - a couple of business days is fine). Encourage commercial users to purchase support. Encourage non-paying users to donate (like Ubuntu, I did donate to them several times). I don't know if you have much commercial usage at this point, but if you do, this might create a recurring revenue stream which will keep you afloat. Or get in touch with someone in Silicon Valley and work out a business plan. What you have right now is by far the best IoT development platform available. It might be not clear to someone without business skill how to make money with it, but I'm sure it can be done.
