You are perfectly correct that your prayers on behalf of your deceased friend are a much worthier subject of meditation than his prayers for you. I would not wish to comment on the state of his soul in particular, but I will tell you this: Hardly anybody goes directly to heaven. Of all the souls that are saved, the vast majority of them will have to spend some time in purgatory, a rather long time as a matter of fact. There are two purposes for this, one penitential and the other remedial. The souls in purgatory have to do penance for any unrepented venial sins and any other sin for which sufficient satisfaction has not been made on earth. Since this aspect of purgatory is purely penal, it can be remitted by God through the prayers and good works of others. This is why it is so important and salutary to pray for the dead.
But purgatory also has a remedial aspect in the sense that souls who are not fully conformed to the image of Christ will learn there, through their sufferings, to will and to want the right things. Any lingering attachment to earthly goods must be stripped off the soul before it can withstand the pure atmosphere of heaven. Souls in purgatory can no longer merit by their sufferings (which is why it is so important to live penitently while still on earth) but they can mend by them. This is the proper work of souls in purgatory, their right and fitting duty, and it would be unhelpful for us to trouble them with our own needs when our prayers would be much more beneficial to them.
Two things to take away from this discussion are these: A) If your friend is saved at all (let us hope!) he is almost certainly in purgatory not heaven, and; B) If he is in purgatory, he needs your prayers a lot more than you need his.
The blessed in heaven can certainly intercede for us and it is noble and salutary to ask for their intercession. They see all things reflected in God and have perfect knowledge and perfect will. But the only way to know for certain if someone is in heaven is if they are a properly canonized saint of the Catholic Church. Catholics are not permitted to offer public veneration to non-beatified persons; however, if you think somebody might be in heaven, you can still ask for their intercession in private prayer.
Whether the souls in purgatory are able to intercede for us (even though it is not advisable for them to do so) is a matter of some theological controversy. Saint Thomas Aquinas says that they do not, at least in the general case, for they have no means of knowing what is happening on earth. Since they have departed the natural world and left their bodies to revert to dust, they have no natural senses; and since they do not yet have the beatific vision, they cannot see all things reflected in God. Thus, they can only perceive such spiritual things as are present in purgatory and whatever else God may decide to reveal to them. This does not preclude that God may wish souls in purgatory to sometimes pray for the living as part of their penance and remediation, but that would be at God's discretion. Whether the souls pray for us, and when and why and how much and who for whom, would all remain for us a matter of conjecture. We do not know it with certainty, hence it is better for us to simply pray for them in charity.