One way to tell is to
take the batteries out of it. If the display stays lit then it is
power stealing, if the display goes dark then it is not power
stealing.

When I do that, the display slowly get dim almost to a point i can't
see it anymore, probably from the internal battery to retain
programming memory. So what does that mean?


There is a note on page 11 that says
*"The remote sense feature will not work if
the system does not provide 24V to the
thermostat (example: millivolt heating-only
systems or 3-wire zone valves).

I don't have either

To use a remote sensor, jumper W922 must be
clipped (see figure 10) and the REMT SEN
option in the configuration menu must be set on."

I have done that

Again, your thermostat does not appear to be power stealing based on
the diagram you provided. You can make it power steal by doing the
following:

1. At the boiler identify the point that the thermostat wires connect
to.

2. Find a terminal labeled "c".

3. Take any spare thermostat wire in the bundle and connect it to that
terminal.

4. Go to the thermostat and connect the other end of the same wire to
the common terminal of the thermostat.

5. In the diagram you provided it appears that the thermostat may not
have a common connection.

If I don't have a C connection, where would the wire connect to?