Wow 4-6 months, that puts things into perspective...we go through the same steps except for the logo design trademark search. Currently we're two devs, looking for a designer and business/marketer. Until then, I wear those hats as well, and we always figured once we get a decent designer on board, we'd have a logo worth pursuing a design trademark for.
You can file the trademark yourself. I would look at all the competitors in the space through trademark searches, see how they define the trademark and the define your own balancing being really broad vs. very exact. If there is a problem in your filing, the attorney at the trademark office will help you out and you don't need to pay anything. They can't advise you on how to protect the name, but they will ensure the wording in form is correct. Actually, I was quite impressed at their customer service!
This is all just my opinion, I am no expert in trademarks. But I love the process of building a name brand. Trademarks are pretty important to avoid complications that you have encountered. Good Luck! Sorry for the woes and I hope you find a really cool name. Luckily .coms are loosing some ground as the ONLY name to get these days.
Try Swahili (East Africa) names, they sound good rolling off the tongue. My steps have always been: Domain Check, Search Name on Internet with Combos, Trademark "word mark." If you can get past all of that, then you need to check for the logo design trademark search. Really, the wordmark is quite important. BUT....another important step now in my opinion is checking for all the Twitter and Facebook URL's too. Trying to brand that one domain with everything... makes it pretty tough huh?
If the domain is not available I move on, else go to the next steps.
I spent 4-6 months trying to come up with a name, but I suppose its different for everyone.