"It is heretical to conclude from that that the nature of the Eternal Trinity somehow changed with the incarnation, "
The nature of the eternal God can not change. Nevertheless, Christ did not have a human body in eternity past - and does now. That is a change.
"I will research which christological error yours is later, if you are curious. "
Thanks, you're always so kind in that regards, finding my heresies for me an all! :)
"So, why exactly command over the created world such as walking on water or through walls is different than omnipresence?"
Christ's resurrected body was capable of many things - instantaneous travel etc. But being in multiple locations at once is a denial of the reality of the body. Christ is one, unified person - not a multiplicity of persons. Additionally there is no Scriptural support for the idea.
Christ did not have a human body in eternity past - and does now. The Real Presence, in any event, refers to the resurrected body, as well as the soul and divinity of Christ. This is represented by dropping a crumb from the Host into the Blood, as separated Host and Blood would represent death.
The scriptural support is, of course, in the treatment of the Real Presence in John 6, the breaking of the Eucharistic bread at the Last Supper, as well as Christ's promise to be with us always, and in particular wherever two or more gather in His name. The distinction you make between omnipresence and other supernatural abilities is wholly artificial: we associate mortality, solidity and weight with bodies as much as spacial compactness, while acts and promises of Christ defy all these properties.