It is obligatory on the husband to sleep next to his permanent wife during the night with amiability once every four nights. It is not sufficient to do so with avoidance and reluctance. He must have sexual intercourse with her at least once every four months in the usual way to satisfy her sexual needs. Not doing so is considered a sin and she can then present her case to the hakim shar'i, i.e. the mujtahid.
The Shias do not have a specific mode of recitation. The Holy book of Allah can be recited by modes of recitation that were common amongst Muslims during the eras of the Imams (peace be upon them). The most popular one nowadays is Asim by the way Hafs, and it is best to keep to this recitation.
It is permissible to purchase a car or any other item by deferred payments for a price that is higher than its current market value. It is essential that the deal is set originally in such a way that the parties agree to the price and the times of installments.
It is not obligatory to remove the dirt under the nail, since this area is not part of wudhu or ghusl. If the dirt prevents water from reaching the skin in parts of wudhu and ghusl, it must be removed; one can use material that removes such substances in the conventional way, and one need not focus on this beyond that. However, if a person has a reasonable doubt whether there is any substance that is forming a barrier between the water and the skin, then he should remove it to ensure that water reaches the skin.