In regard to women, how do we define a service as “leading”?

The scriptures indicate the general principle that women ought not to exercise authority over men nor teach them (1 Tim 2:12). This is partially particularized and defined in 1 Tim 3—viz., women ought not be elders and deacons. On the other hand, the scriptures are also sufficiently vague to allow a certain range of activities. In many respects, it depends on attitude and definition: what is required of the person who leads the Bible study or the worship team? Does he or she need to initiate, control, direct, decide, etc. for the group? One of the things that the NT is clear on is that we are no longer under the case-law of the OT: that is, we don’t need hundreds and hundreds of regulations to figure out God’s will. Now, we live by the power of the Holy Spirit and the guidance of general principles. This is because we are in the inaugural stages of the new covenant (cf. Jer 31 and Matt 26) in which no one needs to tell his neighbor to know God (or his will), for the ‘law’ of God is written on our hearts (which seems to be an oblique reference to the Holy Spirit; cf. Rom 8:2). Therefore, for me to specify which items on your list are a violation of the principle and which are not would itself be a violation of the new covenant principle.

What it is best to do is to examine these things, wrestle with them in light of the clear teaching of scripture on the general pattern of leadership in the church, and then ask whether—in your particular case—such roles seem to violate the spirit of the text or not.