I don't think you're going to get an answer from a lexicon. Rather, look at the overall argument. Paul is speaking of celibacy. He regards it as a good thing, but says that people are free to make a different decision. This isn't a matter of doctrine. It's more like a personal preference. He'd prefer to see people remain single, but acknowledges that it's fine if they don't. So in this case he is simply asking that people treat his judgement seriously, but not claiming it is a command from God. I wouldn't extend this to other types of statement that Paul makes.
Even inerrancy (which I don't believe) doesn't prevent Paul from stating personal opinions, particularly if they are clearly labelled as such.
I don't know that in the context of a pastoral letter it really does make sense for Paul to state a merely personal opinion within the context of inerrancy.
Even so, he is not saying he thinks the Holy Spirit has guided him in the decision to choose celibacy; he is saying he believes the Holy Spirit has guided him in the decision to believe celibacy is preferable to married life but that married life is a morally viable option, at least for those who are too drawn by sexual acts to renounce them entirely.
However, this statement with reference to the Holy Spirit in 7 is made in the context of a greater epistemological argument within the context of the letter. Within the context of this epistemological argument the Holy Spirit reveals directly to individuals within the Church, "so that we can understand the things that were freely given to us by God." (
2:12 ISV). This is most specifically about things pertaining to individual vocation (cf. 1:1; 1:26; 1:28), but the connection between generality and particularity is so great one could not entirely limit it to this, especially because he seems to broaden it to some degree in 13. In this context, St. Paul is claiming, by "I, too, have God’s Spirit" (
7:40 ISV) in the context of a discussion of personal vocation over and above what is revealed in public revelation, that the Holy Spirit has revealed this to him. Given that, it is obvious to me that we must understand "Lord" in 7:10 and 7:12 to mean Jesus in his incarnate ministry and not God simply put, for he is claiming in 7:40 that the Spirit is revealing this.
But the question of the word "δοκῶ" is with reference to his personal epistemic confidence in this claim to personal divine inspiration. Basically, it seems to me (and I believe to some degree Sts. Augustine and Ignatius of Loyola agree with me) that this sort of direct illumination (or whatever you may call it) can only function properly if it is infallible and an infallible capacity on a personal level can only be infallible if it is self referential (that is if it recognizes its own infallibility) or else its infallibility will be tainted by the fallibility of the faculty recognizing it within the context of the individuals epistemic capacities. However, if I read "δοκῶ" correctly, then St. Paul is at least claiming no self referential infallibility.