All three words are derivates of "deka" which is the Greek word for "10" or "10th."
#586, apodekatoo is a present active infinitive. Infinitives use the word "to" to complete their meaning, thus "to take tithes". The present tense denotes ongoing or continual action. This was something the "Levites," not us, did in an ongoing/continual manner. It was an action that fit their present purpose in God's plan, which purpose has now come to fulfillment/completion in Christ.
The "apo" on the front of the infinitive is a preposition, which in this case means "from," thus they received tithes "from" the people. The Greeks like to connect their prepositions on to nouns, and verbs, rather than leave them hanging out there all by themselves, like we do.
#1183 "dekatoo is a perfect active indicative. This denotes an action that took place at a given time, but which had ongoing results. Apparently the writer of Hebrews would have us to understand that Abraham's "one time action" of giving tithes to Mel had long term important effects. It symbolized something that continues well beyond the actual event of giving to him. This is what the writer of Hebrews' whole point is about. What Abraham did had far reaching implications.
#1181 "dekate is the adjective form of deka, and is in the accusative case as an adjective describing "men that die." It's a bit of a complicated Greek construction, but the author is describing these who died. They are a specific subset of men who die. They are "tenth having died men," I.e. men who regularly received the tithe who have now died. It simply describes these dead men as "tithe receivers."
The Levites (not us) were a specific subset of human beings, who were called to receive tithes. If the NT described ministers as Levites, or as those who replaced the Levites but continued their ministry as NT Levitical ministry, then it would be appropriate for them to receive tithes of the NT saints, and thus it would be appropriate for the NT saints to tithe. But, since NT ministers are not the functional replacements of the Levites (I.e. we don't officiate animal sacrifices, care for the literal tabernacle/temple, etc.) they are no longer the rightful beneficiaries of the believers' tithes. However, Paul does say that just as the Levites (of which we aren't) received tithes, and because the oxen who tilled the ground received a portion from the earth's produce, and because a soldier received wages for his labors to protect (three very different analogies to make one point), it is appropriate to financially, materially, and with honor, bless those who teach you the Word of God. As the Levite cares for the natural things of the temple, so the NT minister ministers spiritual things to the living temple of God (you/people). As the ox labored to feed you natural things, so the NT minister feeds you spiritual things. As the soldier protected you naturally, so the NT minister protects your soul from error and false doctrine. Therefore...bless him in whatever way the Father leads, not focusing on the 10th aspect, but on the willingness to give, at the Spirit's leading, to those who feed and nurture your soul.
Good things...!!!
Blessings
Tom