I think I`m getting it; please excuse my rapid responce here as I have to go make some tacos.
What you`re doing is what a lot of people do, so take confidence in how you can succeed and you don`t have to re-invent the wheel! That`s a GREAT thing, but you will also have to make a lot of decisions as there really isn`t a "right" answer and often times it comes down to what works the best for your life.
Here is a
SuN member who can facilitate your inbound and outbound shipping "stuff"; there are a lot of places who offer various inventory, pick and pack, fulfillment etc. ... this gives you the ability to keep all your stuff in one place and get it out in one box; they will also handle all the calls, orders, and other things too ... it`s not a bad place to start if you don`t know anything about anything (not being curt, but logistics and all that jazz can be a major headache in itself).
Here is a
SuN member who is doing something like I think you want, except I think he`s more of a salesperson without a specific brand; they are great people and this is a channel for logo`d product (e.g., he`s a member of the associations I posted in my first responce) as someone who makes a simple product can`t sell on all the people who might desire/need the product; so you join an association where the members sell for you and take a legitimate markup; he may be willing to explain and work more with you kind of thing; it`s hard to know about people and what makes them smile.
Anyway, even Amazon sometimes ships mutiple boxes, some companies never actually take possesion of what they sell, and there are a million ways to do things ... it`s harder when you`re going to have something personalized but the basic thing is to figure out your choke points and keep them under thumb ... nothing is every perfection all the time, but with your business you should be able to find a lot of examples fo the companies you think do a good job and then figure out what makes them "sing" to your brain.