On the Re-entry of an Indian on B2 visa?

If your spouse arrived with you on 12 Dec, her maximum stay is 180 days, which is slightly LESS than 6 months. You need to get her home sooner than 12 June! B2 visa is only valid for one entry, unless you hold a multiple-entry B1/B2 visa. Maximum stay for tourists is 180 days out of any 365-day period, so if you can get another tourist visa, you will NOT get approved for another 180 day period. IF you were to remain in US for 183 days out of any 365-day period, you would become subject to filing & paying US income taxes on worldwide income from all sources. 

Also, you need to beware travel restrictions, which are increasing right now due a surge in cases of covid, including a more virulent variant of covid-19 which has emerged.

Also, if your wife receives any medical care in the US, make sure all bills - doctor, hospital, laboratory charges, & everything else - are all paid in full in cash prior to departure, and KEEP those paid receipts forever! If you fail to pay for any medical care, you & your wife will be permanently barred from the US under Public Charge laws. You are required, as a tourist, to pay ALL your own expenses, especially any medical/health care costs.

In terms of your visa alone that would probably be allowed but if COVID-19 travel restrictions are still in place you could be denied just for that reason. 

Yes, no problem. You can be in the USA for up to 180 days per year on a B2 visa.