Retirement tax questions

I am just beginning to understand the implications of the nondeductible contributions, or basis, so please bear with these novice questions.  So each year that you take out a distribution or do a partial Roth conversion of an IRA, the basis will be reduced by the portion that you calculated is nontaxable? Thus line 14 from the previous year becomes line 2 of the next year?  And Turbotax automatically will prefill line 2?

 

Husband also has a solo 401(k) plan.  Does it require any entries in Form 8606?  Is it inter-related with the IRA with RMDs and Roth conversions?  Or is it an entire separate issue, and separate form?

 

In general how hard is it to file an amended return with Turbotax, can it be e-filed and is acceptance as quick as it is with the original filing?   You mention attaching an explanation, is this something I'd do in Forms mode?  Also if I have a document from rollover of employer plan to the IRA which shows the starting basis, will that be required by the IRS?  Can I simply enter that amount in line 2 of my amended 2019 return (first year taking a distribution)? And it would be great if Turbotax incorporates the amendment in the tax data file so when I start my 2020 return it will have the correct basis, and then for subsequent years will carry it over.

 

I probably will be seeking a CPA since I'm feeling like I'm only discovering the tip of the iceberg and see that we will need guidance in the distribution/management stage of retirement income.   You've given me a good starting point for informed discussion, thanks.