Writing in Dorian is a completely valid thing to do and nothing to be afraid off. Great job on figuring these things out and jumping into advanced music theory! Definitely don't overthink it too much, if the Dorian scale fits the whole tune and the tonal center is B Dorian then that's probably just what it is.
To get a bit into dominant tonic resolutions in Dorian:
In modal music, such as Dorian, cadences have different functions. If we for example take your B dorian tune, the different degrees look like this:
Im7 B-D-F#-A
IIm7 C#-E-G#-B
IIImaj7 D-F#-A-C#
IVDom7 E-G#-B-D
Vm7 F#-A-C#-E
VIhalfdim7 G#-B-D-F#
VIImaj7 A-C#-E-G#
Which makes the V, which normally has a dominant sound in Western tonal music, as you've correctly observed indeed minor. You don't have to go to the I with a dominant chord, like the IV though, if you don't want to. You can approach it in minor from the V or from anywhere else you want. Something I personally really like is approaching it from the IIm7, since that's a uniquely Dorian sound. In the end, in modal music it's more about staying in the tonal center of B Dorian rather than having sub dominants and dominant structures. So the worst thing you can do in a tune that's in B Dorian is take a IV-V-I to A major for example, because you then lose the Dorian sound, despite keeping the same amount of sharps and flats. It's of course still something you can do though, musically speaking, if that's something that you want to do. But for writing Dorian it's a no-go. Play around with these degrees and see how they relate to the I tonic, modes are really interesting and bring many beautiful chordal structures that you lose by thinking too much in old fashioned neo-classical music theory.