Interesting question and I'll try to give an answer to the questions that you state explicitly.

Blood is edible and is eaten in loads of countries. Black sausage comes to mind. However, blood tends to coagulate rather fast and meat needs a fair amount of time to mature. I'm guessing that leaving blood in the meat will give the meat dark spots that are not appealing, therefore the prohibition.

Milk and meat are eaten together at least in Spain. The only reason I can imagine for not mixing them is historical. Originally the Jewish tribes lived in a dessert. A hot climate and food... don't go well together. Maybe milk turned sour fast, or it turned into yoghurt, and maybe that was feared...

All this is just guessing, so anybody that finds a valid reference is welcome to post here.

Interesting question and I'll try to give an answer to the questions that you state explicitly.

Blood is edible and is eaten in loads of countries. Black sausage comes to mind. However, blood tends to coagulate rather fast and meat needs a fair amount of time to mature. I'm guessing that leaving blood in the meat will give the meat dark spots that are not appealing, therefore the prohibition.

Milk and meat are eaten together at least in Spain. The only reason I can imagine for not mixing them is historical. Originally the Jewish tribes lived in a desert. A hot climate and food... don't go well together. Maybe milk turned sour fast, or it turned into yoghurt, and maybe that was feared...

All this is just guessing, so anybody that finds a valid reference is welcome to post here.