You might refer to the HMRC helpsheet HS283
as part of this answer.
The gain on the sale of a property is treated as having accrued evenly over the entire period of ownership so all you need to do is divide the gain by the number of months that you owned it and then deduct the tax free parts to arrive at the taxable part, if any.
Based on what you have told me, the gain for the period between the date you bought the 1983 property to the date you moved out in 1993 should
be exempt as it was the only property you owned and you will certainly get exemption for any part of that ten years that you actually lived in it. However, whilst you had no financial interest in the rented accommodation, in the absence of a main residence election, it can be treated as your main home based on the facts, ie where you lived for those ten years. This could scupper your CGT exemption for those ten years.
Take a look at the notes in CG64500 here
. You might consider making a nomination now for the 1983 property to be treated as your main residence until 1993 under Extra Statutory Concession D21.
The gain for the period from the date in 1993 that you bought another property (which you nominated as your main home) until 1996 will be a taxable gain as will the gain for the period from the date in 1996 you bought the property with your husband until its disposal in 2010.
When you put your husband's name on the deeds of the 1983 property, he took your purchase date and half the purchase price as his own for CGT purposes.
You moved into the 1983 house in 2010 so from that point it will be treated as your main home assuming you have no other property. The gain for the period between your moving in, in 2010, and when you sell it or up to three years after you move out will be exempt from CGT.
If there is any taxable gain after you have extracted the gains for the exempt periods, each of you and your husband will be entitled to utilise the annual CGT exemption which currently stands at £10,900. That will cover at least £21,800 of any taxable gain.
I hope this helps but let me know if you have any further questions.