I’m sure you are looking at two different people as a Type Founder would be unlikely to train as a doctor. You can usually trace the career of Doctors/Army surgeons via the various Gazette publications at http://www.gazettes-online.co.uk/ , although not online [google for sources] you should be able to trace him via the various Army Lists to establish what became of him.

Here’s a few as examples from the London Gazette:

London Gazette 20 September 1839
Hospital Staff
To be Surgeons to the Forces.
Surgeon Alexander Sinclair, M. D. from the 25th
Foot, -vice John Glasco, who retires upon halfpay.
Dated 20th September 1839.

November 1844
HOSPITAL STAFF.
Staff-Surgeon of the First Class Alexander Sinclair,
M.D. from half-pay, to be Staff-Surgeon of the
First Class, viee Francis Arthur Macann, M.D.
who retires upon half-pay. Dated 29th November

London Gazette 9 February 1848 Stamps & Taxes Copy of Banker’s Returns
National Provincial Bank of England

On page 486
Sinclair, Dr. Alexander; Residence: Fort Pitt, Chatham; Occupation: Staff Surgeon.

London Gazette 9 February 1855, Appointments
Page 493
Hospital Staff
To be Staff-Surgeons of the First Class.
Staff-Surgeon of the First Class Alexander Sinclair,
M.D., from half-pay, vice Hart, deceased.
Dated 9th February, 1855.