FYI: BPR-3, Para 7.4 indicates that typical range of VLPFM (Very Low Power FM, 10-W Max ERP) is just 2 km....which may or may NOT meet your needs, in which case you might want to look at LPFM (Low Power FM, 50-W Max ERP), which is limited by Line-Of-Sight, with a range that MIGHT be as much as 10's of km's.
You/We should investigate these claims a bit further, esp. since your viewers would be using a variety of FM Radios with Sensitivity ranging from Good to Poor, esp. given that most would NOT be using even Mediocre Indoor Antennas, such as Rabbit Ears or a (two-arms-length) Folded-Dipole....and few would want to install an Outdoor Antenna. [And bear in mind that Antenna Gain for a typical Indoor FM Radio is significantly NEGATIVE due to it's size....and typical Indoor Loss MIGHT be as high as 20 dB.]
For comparison, FCC estimates that a 100-W ERP LPFM Station (in US) would have a "service range" of just 5.6-km [which would INCLUDE a predominance of Listeners with Indoor Radio/Antennas]:
You should contact OTHER Religious Broadcasters in your area to build on their experience. I tried to find some GROUPS that could help you, but didn't immediately find any in your area. However, I did find the fol. [somewhat out of date] re. Special "Balance" Rules for Licensed Religious Broadcasters, which you MAY need to know (esp. HOW to meet the "Balance" Rules):