We present new MUSE/VLT observations of a small globule in the Carina HII region that hosts the HH 900 jet+outflow system. Data were obtained with the GALACSI ground-layer adaptive optics system in wide-field mode, providing spatially resolved maps of diagnostic emission lines. These allow us tomeasure the variation of the physical properties in the globule and jet+outflow system. We find high temperatures (T-e approximate to 10(4) K), modest extinction (A(V) approximate to 2.5 mag), and modest electron densities (n(e) approximate to 200 cm(-3)) in the ionized gas. Higher excitation lines trace the ionized outflow; both the excitation and ionization in the outflow increase with distance from the opaque globule. In contrast, lower excitation lines that are collisionally de-excited at densities greater than or similar to 10(4) cm(-3) trace the highly collimated protostellar jet. Assuming the globule is an isothermal sphere confined by the pressure of the ionization front, we compute a Bonnor-Ebert mass of similar to 3.7 M-circle dot. This is two orders of magnitude higher than previous mass estimates, calling into question whether small globules like the Tadpole contribute to the bottom of the initial mass function. The derived globule properties are consistent with a cloud that has been and/or will be compressed by the ionization front on its surface. At the estimated globule photoevaporation rate of similar to 5 x 10(-7) M-circle dot yr(-1), the globule will be completely ablated in similar to 7 Myr. Stars that form in globules like the Tadpole will emerge into the HII later and may help resolve some of the temporal tension between disc survival and enrichment.