Testing - Black Berry Jam Pie

Some of the recipes I Frankensteined this one from instructed to separate the eggs and make a meringue with the whites and 3 Tbsps from the sugar. I want to see what it would be like to simplify it and just put in the eggs.
1 - WAY too sweet. The amount of sugar to add, if any, is dependent on the sweetness of the jam, so it has to be to taste, with an explanatory note; I am thinking that making a custard pie should be enough - egg yolks and no egg whites - still not sure about adding a soft meringue on top; the flour is essential or the pie is too wet. Looking forward to trying it with crème fraîche, although I think its tang is very close to that of the buttermilk, making it a great candidate for using up extra buttermilk; I suspect the cooking time is too long, since the crust went in unbaked and came out almost burnt, and the custard itself was quite an unattractive sort of purple-brown.

4 eggs
1/2 1/4 cup sugar TO TASTE - depends on how sweet the jam is
1/2 cup butter
1 cup blackberry jam
1 cup buttermilk (or crème fraîche )
3 Tbsps flour
1 tsp lemon zest or vanilla
small pinch of salt
pie shell

1. Just mix it all together and pour into the unbaked pie shell.
2. Bake at 350F 325F for 45 30 minutes