First the penalties have to be formally assessed, whether they have been estimated
and paid or not. The amount you paid may be too high or too low, depending upon which penalties are assessed & how much interest is charged; then whether you owe anything additional or are due a refund will depend upon which penalties are abated & which ones may not be abated.
The tax attorney/CPA in this case is acting as the tax preparer
for the LLC. I presume that as an attorney he's smart enough not to "go against" (as you put it) a member of his own client, ie. you as a member of the LLC. Besides, there's nothing to "go against" you about; so you didn't review the returns before you signed them but chose to rely on the CPA who prepared them; in reality, that happens every day; despite admonitions to the contrary, most clients do not review the tax returns in any detail; they simply don't know what it all means; that's why they hire us
as experts; so again, don't worry about it, that's not going to happen.
As far as what role the attorney might play as a tax attorney depends upon what he is hired to do and what his experience is; most attorneys don't litigate; it depends upon the circumstances; as a minimum they would be able to represent clients with the IRS if engaged to do so; I really don't think there's much actual risk of any civil or criminal proceedings involving you under these circumstances. The only one that should be concerned is the CPA who prepared the original LLC returns.
Honestly, it's clear to me that your so-called partner doesn't understand, who is responsible for what when it comes to the LLC. For whatever reason, he evidently enjoys "cranking you up" & apparently he has done a pretty good job of it. It's too bad; there must be some other motive involved here and only you would be able to
determine what that may be.
You really need to go forward and figure out how you are going to re-establish a working relationship with your "partner" or I'm afraid that when your pre-school
starts operating, you'll be in for one problem after another. If you determine that it will be impossible to work with this guy on a going forward basis, there are steps you can take to have the assets
of the LLC liquidated and divided among the partners.
If that becomes a reality, you'll need to discuss your options with a local
attorney & once you make your intentions known, your "partner" will find out that you have just as much control over things as he does and either he will straighten out, smoke a peace pipe with you, or subject himself to the ramifications of dissolution of the partnership or be forced to buy you out at the fair market value of your interest in the LLC & partnership.