He is already on an ADSL Max line, you can tell this as his Operational Mode/Modulation is set to G.DMT - this is ADSL Max.
BT's dynamic line management will only bump your IP profile up if you hit the threshold for the higher line profile and keep that sync for up to 120 hours (max) - it can be as quickly as 4 hours if it's a significant increase however going from ~3500kbps to ~4500kbps will take quite a few hours. Kitz has a very good explanation on the whole process here:
http://www.kitz.co.uk/adsl/IPprofile.htm including a list of IP profiles.
As your line isn't stable right now go to the SNR Tweak page (
http://192.168.1.254/snr.cgi) and change the value to 50. This drops your Target SNR by 3dB and will hopefully be stable. Also, go to the ADSL Mode page (
http://192.168.1.254/configuration/adslmode.html) and make sure you have PhyR ticked for Upstream and Downstream - this will hopefully keep your line more stable at lower SNR values. It should look like this:
tl;dr: don't keep on rebooting your router, your actually making the problem worse by doing this as the BT equipment will think you have a flakey line. Make the changes to the SNR and ADSL Mode I suggested and wait it out until BT reset your IP profile
if you hit the threshold for the next IP profile.