Yes, there is an index to the compiled service records of Mexican War soldiers. It is on microfilm M616 at the National Archives. In this case, you know that he served in the Mexican War, because the patent certificate that you found at the Bureau of Land Management website is a military warrant, and it names the regiment that he served in. The compiled military service record is not going to tell you anything about this land. Bounty land was a reward for military service, but it was something that the soldier had to apply for. There will be a bounty land application file at NARA (unless he was pensioned, in which case the BLW application will be filed in with the pension papers). There will also be a surrendered warrant.
Your soldier did not get land in Wisconsin. What he received was a bounty land warrant, which was a piece of paper that could be exchanged for a land patent anywhere of his choosing on the public domain. Your soldier sold this piece of paper to a third party who is named on the patent certificate as the "assignee" of your soldier. This is the person who actually chose land in Wisconsin and patented land there. At the BLM site, the "w" next to the name is the "warrantee", in other words, the soldier who received the warrant. The "p" next to a name is the "patentee", the person who actually patented land with the warrant. The patentee might be the soldier himself or somebody else. In your case, it is somebody else who got the land in Wisconsin. The surrendered warrant file at NARA would contain the actual warrant certificate, showing the sale of same on the reverse side of the document, similar to how we might sell our car by signing the back of the title over to someone who has purchased it.
The most information you will find on this soldier would be in his pension file if he was a pensioner. The pension index is also at NARA, but I believe there are printed versions of it. I can't tell you where to find those, since I always look at the microfilm indexes in person at NARA. If there is no pension, he definitely has a bounty land application file, as well as a surrendered warrant file. His compiled military service record would not give you any personal information about him, only his military record of enlistment, discharge, pay, any promotions or disciplinary actions, and whether he was present, absent, sick, or AWOL.
I don't know how old your soldier was, but sometimes young soldiers of the Mexican War went on to become older officers in the Civil War. You might want to check the soldiers' and sailors' website at: www.itd.nps.gov/cwss
and see if you find your soldier in the Civil War. If he was in Louisiana during the Mexican War, you might find him in a Confederate regiment.