.....added to bosse's question of where does your mom stand?
I wholeheartedly agree that the main problem is the age difference, you are still just a kid to him, and he knows what he's doiing. That probably isn't going to change soon, if ever. Five generations of doing the same thing, because it always worked before, is a tough nut to crack, ( and unfortunately the downfall of many a florist). Added to that the fact that it is very difficult to accept an adult child's opinions as better than your own, and you have quite the hill to climb.
I will say this.....in the stuffing area. You cannot change what product the customers are used to overnight. As Boss said, you would be much more effective going in the side door. Not just with your step-dad, but with the customers. All people are adverse to change, especially as we age. You clearly in your mind are doing what you know is best for the shop dollar-wise on the stuffing issue. HOWEVER, this needs to be approached gradually, not in-your-face. Remember, these customers were used to the stuffing, they REALLY DON'T CARE if it is detrimental to the shop, they want what they are used to.
You are going to HAVE to learn to compromise with a genuine attitude of good will. If you stubbornly refuse to put more flowers in than what the customers will pay for, they will continue to be driven away. You need to put them on a VERY GRADUAL DIET. It's like putting a dog on a diet. If you just suddenly take away a quarter of a cup of food each day, they are going to feel deprived. Same with your customers, same with step-daddy. You take one flower away at a time, over a period of time. You will do more to save the business that way.
Definately get SOMEONE to do the math on the wire service thing. If you are bringing in ANY sort of profit, I would hesitate to drop it until you have re-developed a good local custom again. Every shop needs to do their own math on this issue, it isn't a one size fits all type of thing. I know what you are talking about with 800, no, they don't give a rats a$$ about you, they just need to keep revenue coming in to appease their shareholders. But if it makes sense to keep your inventory fresh, then now is not the time to drop them, just keep moving toward that goal.
I remember being that age, vaguely......everything was important and need to be acted upon immediately. So put yourself on a gradual diet as well, make it clear that you respect your step-dad's knowledge. Believe me, he knows a lot! I understand your frustration in wanting to move things along, but you MUST take to heart how very difficult it is to get everybody around you to change to your way of thinking over-night.
Patience and gradual change is the only way....seriously.....You could end up driving things into the ground faster by trying to do things THE RIGHT WAY, than if you take a more casual stance. I wanted my own shop from the time I was 13 years old, it was all I ever dreamed of. I finally opened my own when I was 36. I can honestly say that had I not gained a whole lot of experience in other shops, and just opened up in my twenties when I wanted to, I would have failed miserably.
So my advice, fwiw, is to learn all that you can, absorb the info you can glean, and try very hard for compromise. Definately DO NOT go down a road that will sever family ties, it's never worth it. What is wrong with continuing to build the wedding business through the family shop with your name? I've worked at shops where the designs had "Designed By....." along with the price tag. This would be a clear indicator as to what your customers are looking for.
Finally, do you know the 12-step program's prayer? Even if you don't believe in a higher power, the wisdom still holds true. Someone help me out here, because I don't know it by rote, but it helped me when I needed it. Something about courage to change the things I can change, humility to accept the things I cannot change, and the wisdom to know the difference.
I want to see you grow, the best managers learn to take baby steps. You have to remember that your step-dad has been around since you were in a crib, for crying out loud. You need to get him to respect you, and that will happen more swiftly if you emulate him WITHOUT ATTITUDE. Fine, fine....that sounds like you are humoring him, (which I know you are, ) but so does he and so he probably feels you lack respect for his wealth of experience.
Just try to compromise for now, and continue to build your own identity. I have more, but I will leave it here for now. Patience!!!!!!