All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The wife is obliged to obey her husband if he calls her to bed, whether she is pregnant or not, unless she has an excuse such as menstruation, obligatory fasting, illness, or that intercourse harms her or her fetus. As for mere fear or worry about the fetus without justification, then this is not an excuse.
Mar'ee Al-Karmi said in Daleel At-Talib: “The husband may enjoy his wife at all times, in any manner as long as it does not harm her or obstruct her from religious obligations.” [End of quote]
Each spouse has the right to enjoy the other spouse’s body as he likes, except for that which the Sharee'ah forbade, such as intercourse in the vagina during menstruation and anal sex; Allah Says (what means): {They are clothing for you and you are clothing for them.} [Quran 2:187]
There is nothing wrong with a husband being masturbated by his wife's hand.
Al-Hijjawi said in Al-Iqnaa’: “He [the husband] is permitted to masturbate with his wife’s hand.” [End of quote]
As for knowing the safe times for intercourse during pregnancy, then this is not our specialty; you may refer to the doctors in this regard.
Allah Knows best.