Does seeing "that is the Book, in which there is no doubt" in a dream after performing Istikhara regarding having a male child mean not getting pregnant again?

We do not have specialists in dream interpretation. Regarding increasing progeny, the default is for a Muslim to strive for it unless there is an impediment. Therefore, you should endeavor to increase progeny and have a good opinion of Allah. There is no need for istikharah (guidance prayer) concerning this matter, as it is desirable in Islamic law. Jurists have explicitly stated that a man is prohibited from practicing azl (coitus interruptus) with his wife without her permission. It is reported in the hadith: "Marry the affectionate, fertile woman, for I will boast of your numbers before the nations." And in another narration: "Marry and procreate, for I will boast of your numbers before the nations on the Day of Resurrection."