If being in heaven were like being in the next room, then of course these objections would be valid. A mortal, unglorified person in the next room would indeed suffer the restrictions imposed by the way space and time work in our universe. But the saints are not in the next room, and they are not subject to the time/space limitations of this life.
This does not imply that the saints in heaven therefore must be omniscient, as God is, for it is only through God’s willing it that they can communicate with others in heaven or with us.
The Bible directs us to invoke those in heaven and ask them to pray with us. Thus in Psalms 103, we pray, “Bless the Lord, O you his angels, you mighty ones who do his word, hearkening to the voice of his word! Bless the Lord, all his hosts, his ministers that do his will!” (Ps. 103:20-21). And in Psalms 148 we pray, “Praise the Lord! Praise the Lord from the heavens, praise him in the heights! Praise him, all his angels, praise him, all his host!” (Ps. 148:1-2).