First opinion.... Far too many of us woodies get over-involved with angles and sizes. Advice .... leave all that precision to the engineers who are working with material with little or no movement or 'give'. Experiment and If a technique works... use it again!
Second opinion... where possible always use a chuck in contracting mode. The alternative has you turning away the wood away, reducing its inherant strength, while the chuck is doing its best to drive the grain apart.
Third opinion ... a bowl, as drawn, with a base size around 1/3 its diameter will look elegant at the cost of stability whereas one with a 2/3 base will be far more likely to be used. Advice... decide if you making an ornamental piece, or one intended for useful service BEFORE you start.
Fourth opinion ....aside from proper names there are no facts in woodyturning..... only opinions, no matter how strongly those opinions are believed.
Look forward to hearing your views
Brian