TWS API tickOptionComputation() returning positive theta for American option

[BinaryAlgorithm]

For deep ITM put options on a high div yield stock:

field=13 iv=0.160 delta=-0.9988 optPrice=7.52 gamma=0.00193 vega=0.00067 theta=0.00111 und=17.36 pvDiv=1.114

Same theta as reported in TWS. I am trying to figure out how to delta hedge another position with minimal time decay, but it is unclear how this option will behave over its life. I want to estimate the price effect (time decay) of the DTE going from 220 to say 30 or 60 before I roll the hedge.

 

[BinaryAlgorithm]

BjerksundStensland is showing a decay rate of about 0.0045 / day. Does this mean IB only implements the European options model?

 

[arbs-r-us]

For deep ITM put options on a high div yield stock:

field=13 iv=0.160 delta=-0.9988 optPrice=7.52 gamma=0.00193 vega=0.00067 theta=0.00111 und=17.36 pvDiv=1.114

Same theta as reported in TWS. I am trying to figure out how to delta hedge another position with minimal time decay, but it is unclear how this option will behave over its life. I want to estimate the price effect (time decay) of the DTE going from 220 to say 30 or 60 before I roll the hedge.

Obviously this is a deep ITM put. What you are ignoring is the carry (underlying+put, or more easily STRIKE). Suggest a book, options pricing theory, 101.