SPOILER!!!!!
Yes. Yes. No.
I read some spoilers in another website so I may be wrong
What! I want Luka to be their baby!!!!!!!
Spoiler
They will fall inlove eventually, but i read somewhere that it was actually love at first sight for rudiger, thats why he acts differently to FL. FL likes Rudiger coz of his looks, but eventually fell in love with him sincerely when she realized she treasures all the memories she shared with him. (it was actually very funny how he go about courting her persistently after he realized it as actually love he felt for FL.)
They do get married after some cliche opposition from basically all the powerful figures in their country(current king, former king, Luca)
They did not adopt Luca, but they might as well since he inherited the count title FL has when FL married ML and became Duchess and their child calls Luca big brother rather than uncle(luca wanted to be called uncle)
Please tell me they fall in love. Please tell me they get married. Please tell me that they adopt luca as their actual kid.