I don't think to add credit reversal to output tax in table 3 but reverse in Table 4 under other reversals and avail input credit in Table 4 after making payment of tax
As per the provisio in section 16 of GST, read with Rule 37(2) act , it's to be added to Output Tax Liability if not paid within 180 Days & As per Rule 37(2) reversal need to be done in GSTR .2, but as of now it's not being in force , so reversal is to be shown under table 4(b)(2) of GSTR 3b
if partial payment is made reversal will be proportionate to the amount not paid to the supplier. As per Sec 16(2), the recipient later makes the payment to the supplier. If supplier has paid full tax to the government.