Hi Mastiff,
Glad to hear you got your D/L's straightened out. Yes in SPM 1.5 Beta they changed the training missions to use the T-34/76 rather then the Matilda, which is probably a good thing since the the Matilda was really underpowered for the driving course. As for the problems with the Graviteam site, check your Internet security setting they might be too high or something in your Malaware is giving you a false positive. You should be able to "exception" the site in you malaware program also most of the RU sites will give you this same warning for some reason, it's another reason why I started the SFK42 Mediafire file site, those files have been scanned and shouldn't cause any warning flags from your security software.
Now about your fps problem, your rig is pretty close to mine except you have a better video card. On my rig in stock missions fps usually are at 59~60 fps with v-sync on. The only time my fps drop (into the mid 40's) is when playing a senerio that has massive amounts of action like Rends Prokho missions, there is another mission maker named friniks at Graviteam forums, his missions are only available directly from him but they are like armored armageddon and my fps will dip into the high 20's. Kyths missions are a good middle ground, a good amount of action (and suprises) but fps are always pretty high (50ish). So taking this into consideration I would suggest the usual checks first like your drivers up to date and see if your HD needs defraged. If this is all current then all I can suggest is a complete reinstall of SFK42, it's quite possible something got corrupted when you were trying to install the mods. Also even here there is an alternative, if you used the original SFK42 default install:
C:/ProgramFiles (x86)/Lighthouse/SteelFury
just do a new install to:
C:/Lighthouse/SteelFury and try your mods in this new install. If things are working uninstall SFK42 from ProgramFiles (x86)
Also I don't know what version of Windows you use but if its Vista or Win7 I would suggest using the:
C:/Lighthouse/SteelFury pathway as it will cause less problems with the mods and Windows UAC.
When you get finished your JSGME activation box should have these mods activated:
- SPM 1.5 Beta
- Any User Made Missions (like Kyths Missions and Rends Missions etc)
- SPM 1.5 Ultimate (with this new SPM you do not need the SPM 1.5 Beta fix, SPM 1.5 Beta English patch, Widescreen Bug fix, and probably a few others)
- Sound Mod if you use them. NOTE: Only the Steel Sound Mod Collection has to be installed before SPM 1.5 Ultimate
- Any season mods if you use then (like Lajacks Autumn Mod)
- Unofficial english patch v0.1. There is some debate about installing this patch first or last, but either should be okay (I have it installed last). If you install last you will get a warning from JSGME that the unofficial patch will want to overwrite 2 files in SPM 1.5 but don't worry as I have seen no ill effect from installing last, but you have to have this patch installed no matter what as it fixes a bug in SFK42 where your tracks come off if you press the "T" key.
One final thing about your cropped UI, the Widescreen Bug Fix is a hit or miss fix, for some people it works on their monitors and others (like myself) it doesn't work.

P.S. Another final note, Kyth has advised installing User Made missions after SPM 1.5 Ultimate for a couple good reasons, so while no problems have been reported following the install proceedure in SPM 1.5 Ultimate readme to date (what I listed above) it is an important option to consider.