Is it permissible to recite Surat Ya-Sin 41 times and put it in water to drink for ease of affairs, as mentioned in the book "Shams al-Ma'arif"? Are there legitimate Islamic ways to make a wife love her husband, and is what is called "love paper with Quranic verses" halal or haram?

The optimal means for love between spouses is their adherence to Allah’s Sharia. For the obedient one, Allah loves him, answers his supplication, and makes him beloved to His creation.

The Messenger of Allah, peace and blessings be upon him, said: "If Allah loves a slave, He calls Jibreel (Gabriel): 'Indeed, Allah loves so-and-so, so love him.' Jibreel then loves him and calls out to the inhabitants of the heavens: 'Indeed, Allah loves so-and-so, so love him.' Then the inhabitants of the heavens love him, and then acceptance is placed for him on Earth."

And in the Hadith Qudsi: "Whoever shows enmity to a beloved servant of Mine, I shall be at war with him. My servant does not draw near to Me with anything more beloved to Me than what I have enjoined upon him. My servant continues to draw near to Me with supererogatory acts until I love him. When I love him, I am his hearing with which he hears, his sight with which he sees, his hand with which he strikes, and his foot with which he walks. If he asks Me, I will surely give him, and if he seeks refuge in Me, I will surely grant him refuge."

Among the permissible means are also: good companionship, patience in the face of harm, repelling evil with good, spreading greetings of peace (salam), and exchanging gifts.

Allah Almighty says: "And live with them in kindness."