I guess that we Reformed Baptists mist believe a different sort of credobaptism then, because no matter how many times you tell me what we believe and no matter how many times I assure you that is not what I believe, it is still not about replacing "and" with "then" or about a "magic age X".
It is about obeying scripture and responding to the call of God, yourself, rather than choosing to respond on behalf of someone else. It is about baptism being more than admission to the visible church in hopes of some day wanting to join the "hidden church". It is about a total package of events that BEGINS with God's drawing, not with man's decision to sprinkle water on a baby that cannot even speak, it is about obeying the command to repent and it is about receiving the Holy Spirit ... all of which are not linked together in Baptist Theology, but in the very scriptures you dissect and pull apart to borrow a piece from here and a phrase from there and ignore everything in between. It is about baptism being a sacrament, not a human ritual, and the participant should make the decision to respond to the drawing of God. Other people should not make that decision for them.
It is and, not the Lutheran "OR". Baptism and salvation. Baptism and God's calling. Baptism and the Holy Spirt. Not baptism and maybe God will call them.
Any age is acceptable. If a 3 month old can indicate a desire to serve God, then Baptize them and allow them to take communion and praise God for another soul drawn into the Body of Christ. If a 50 year old man has no interest in the things of God or being baptized, then he should not be. It is NOT about age, it is about calling, about grace received and man's response. It is also not about order, it is about a list of things that belong together.
In short, it is not the NT covenant of the Household that I reject. I reject the repurposing of the baptism of repentence for a fleshly circumcision on a covenant that is in every other way Christ centered and spiritual. The supporting verses are tenuous at best. Nothing else was left so unclear.