yes you need separate accounts, if you both use the same account, the last one prepared will overwrite the first which will no longer be available.
for you to file as head of household 1) you and your spouse must have lived apart for the last 6 months of 2021and 2) you must also have paid more than1/2 the cost of keeping up a home for yourself and your child or children at least one of which qualifies to be claimed as a dependent by you and lived with you for 6 months in 2021.
failing either rule leaves you with either married filing jointly or married filing separately
do you live in a community property state because income allocation may be needed see IRS PUB 555
if you can't file as HOH, MFS is usually the worse way to file because of various limitations and lost credits.
