Alright, with no light meter, problems using the built-in meter on your Ftb, a film that's not a true 400 speed to begin with (more like 200-ish) and the intention to move to a developer that is even less capable of extracting shadow detail from your film, you've been setting up for a perfect storm. The suggestions for improvement then are obvious:
1: Learn to use the meter in your Ftb (it likely works fine, but you'll have to understand how it works) or acquire a different camera or meter and learn to use that. Without understanding how to meter a scene, you're pretty much lost.
2: Use a film that's reasonably fast. A 400 speed film is fine, but preferably use one that actually hits that speed; let's say something like Kodak TMAX400, Ilford HP5+ or Delta 400. These are safe bets that actually give good shadow detail when rated at their box speed of 400.
3: Use a developer that's reasonably good at extracting shadow detail from your negatives. R09 and other rodinal variants are known for the exact opposite; if you use any of these, I'd suggest overexposing your negatives by half a stop or a full stop to compensate for this. A developer like XTOL, on the other hand, will do better in this respect. Your Eco Pro developer, which likely is a Phenidone-Ascorbate developer, is also a good option.
Evidently, getting this done is 90% knowing what you're doing and 10% materials. So item #1 is by far at the top of the list, followed at considerable distance by the others.
1: Learn to use the meter in your Ftb (it likely works fine, but you'll have to understand how it works) or acquire a different camera or meter and learn to use that. Without understanding how to meter a scene, you're pretty much lost.
2: Use a film that's reasonably fast. A 400 speed film is fine, but preferably use one that actually hits that speed; let's say something like Kodak TMAX400, Ilford HP5+ or Delta 400. These are safe bets that actually give good shadow detail when rated at their box speed of 400.
3: Use a developer that's reasonably good at extracting shadow detail from your negatives. R09 and other rodinal variants are known for the exact opposite; if you use any of these, I'd suggest overexposing your negatives by half a stop or a full stop to compensate for this. A developer like XTOL, on the other hand, will do better in this respect. Your Eco Pro developer, which likely is a Phenidone-Ascorbate developer, is also a good option.
Evidently, getting this done is 90% knowing what you're doing and 10% materials. So item #1 is by far at the top of the list, followed at considerable distance by the others.