There is no problem taking LDN together with 6mp.
Many on this very forum started out taking one of the biologics, and added LDN to their meds, and thereafter were able to wean themselves off the biologics and stay on the LDN - in remission - and doing great.
As far as fillers, some can be an issue for people, these are: lactose, avicel, slow release. And that's the reason I always recommend getting the hypoallergenic filler which is sucrose.
As far as whether oral vs. transdermal and which is more effective, this is very individualized. Some of us do great on oral LDN, and others of us who have absorption issues need the transdermal LDN.
I am happy to hear more doctors are open to prescribing LDN.
That's good news.