Going cheap on the cable is somethng that may not appear ot be an obvious problem. I ran DMX for years on XLR cabling and it worked fine(even a 200-foot run), but that's not going to cut it for me anymore.
DMX cabling isn't that much more expensive than XLR cabling, with costs being in the DOLLARS for large-ish orders(say, around 300-feet of cable, less than $5 price difference on average in my experience and that price difference can swing either way).
Ordering a splitter is going to help but won't resolve your issues if you're NOT willing to buy the right cabling. It may help, but if you're willing to spend money on a splitter, why the hell aren't you willing to spend money on proper cabling?
It's like "Gee, I'm gonna get a super fast router and switch, I'm gonna spend $5 million on my corporate networking hardware infrastructure and we're gonna keep the same old Cat3 wiring that sucks for our phone lines and existing network instead of upgrading our cable plant as well" sort of idea that you're doing.
Then again, I have clients who will spend money to "Do it cheap" and then spend 10 times on the same issue to "get it done right" in the first place, instead of spending an additonal 5-20% in the first place to get the right stuff in the first place.
Plus, since you're investing in a splitter, and you've already ordered it, my advise is for nothing. The OptiBranch/4 has the additional advantage of not only being a splitter, but a 3 to 5 wire converter AND an optical isolator, thus ensuring problems in any branch shouldn't affect the the other brances, as well as making sure problems don't feedback down the line to your dongle, thus protecting your equipment and investment.
Sorry, but forgive my negative association with churches. Here, they've become business and they are tax evasion institutions. If churches are being bought and sold, going under and the like, trust me, this is about MONEY, ESPECIALLY when they are making churches from spaces formerly used as commercial storefronts. Couple that with bible thumpers roaming my neighborhood and ringing doorbells ar 7AM when I'm trying to sleep after pulling a 48-96 hour run of work. And they get all p*ssy when I have a weapon with me I am ready to use upon their person.
Here's the bottom line:
If you do it right, it may cost more short term, but costs less long term, and in some cases, long term savings can show up within 3 months. Have those over you chew on that a while. It's for the benefit of all involved to do it right.