Your Thomas Wills b 1803 was an early Australian Pioneer and is listed in the Pioneers Book at The Melbourne Library. There would be copies of the book in other states as well.
On the N.S.W birth, death and marriages it lists a Thomas Wills b 1803, son of Thomas Wills of Devon, England, with the mother listed as Ann Burrows and m 1795 in Devon, England.
On my Devon Indexes I found 3 Thomas Wills' with anyone of them a possible father to your Thomas b 1803.
They are Thomas Wills b 1774 m Ann Shilston at Exeter, Devon on 23-4-1796.
Thomas Wills b 1776 ( early Australian Pioneer ) m Ann Burrows at Tiverton, Devon on 06-07-1795
Thomas Wills b 1777 m Elizabeth Tucker at Stokeinteignhead, Devon on 19-05-1798.
A thorough search found no children born in Devon to any of the above which could suggest they all may have come out to Australia about 1800.
It is also a possibility that all are related as the places in Devon are all close together.
Let me know what your thoughts are and I may be able to pursue this matter a bit further.