That'a a valid test using a slave battery to power the in-tank pump and no, you won't damage the pump.
The tank seal can be obtained easily from Volvo (about £11) and you could try Rock Auto for the pump.
https://www.rockauto.com/
Last in-tank pump i knew of that came from them was a couple of years back and was about £35 all in including Import Duty - price may have changed because of HMRC but shouldn't be a million miles away. Give me a shout if you have difficulty finding the pump, they only got the 940 until 1995 stateside and then not all models but without knowing what yours is, not sure which pump to suggest that would work.