Yes, it seems definite that there was no Sevale & Haghen, and two different roses were involved. 'Marie Louise' seems certainly to be the centifolia-damask hybrid, which was said to have been bred by "Unknown Dutch breeders before 1811". As Belgium did not exist as a separate country at the time, Brussels was also in the Netherlands.
Yes, the region was Spanish until 1713, then Austrian until 1795, French until 1815, finally Dutch until 1830, when the catholic south revolted and formed an Independent state.
