Hello Dominic, thank you for the try.
I completed the steps you mentioned. Sarted in Safe Mode, then reseted the SMC, then ran the Repair Disk utility (the disk is ok and didn't need repair).
However, the situation is much worse now after these steps. The computer hangs much more often and for much longer. It is not possible to work like this.
Here is the EtreCheck report, hope it sheds some light on the situation.
EtreCheck version: 2.1.8 (121)
Report generated 13 Apr 2015 14:29:35 WEST
Download EtreCheck from http://etresoft.com/etrecheck
Click the [Click for support] links for help with non-Apple products.
Click the [Click for details] links for more information about that line.
Click the [Adware! - Remove] links for help removing adware.
Hardware Information: ℹ️
MacBook Pro (13-inch, Mid 2012) (Technical Specifications)
MacBook Pro - model: MacBookPro9,2
1 2.5 GHz Intel Core i5 CPU: 2-core
16 GB RAM Upgradeable
BANK 0/DIMM0
8 GB DDR3 1600 MHz ok
BANK 1/DIMM0
8 GB DDR3 1600 MHz ok
Bluetooth: Good - Handoff/Airdrop2 supported
Wireless: en1: 802.11 a/b/g/n
Battery Health: Normal - Cycle count 282
Video Information: ℹ️
Intel HD Graphics 4000
Color LCD 1280 x 800
System Software: ℹ️
OS X 10.10.3 (14D131) - Time since boot: 0:36:31
Disk Information: ℹ️
TOSHIBA MK5065GSXF disk0 : (500,11 GB)
EFI (disk0s1) <not mounted> : 210 MB
Recovery HD (disk0s3) <not mounted> [Recovery]: 650 MB
Macintosh HD (disk1) / : 498.88 GB (374.20 GB free) - 43 errors
Encrypted AES-XTS Unlocked
Core Storage: disk0s2 499.25 GB Online
MATSHITADVD-R UJ-8A8
USB Information: ℹ️
Apple Inc. FaceTime HD Camera (Built-in)
Apple Computer, Inc. IR Receiver
Apple Inc. BRCM20702 Hub
Apple Inc. Bluetooth USB Host Controller
Apple Inc. Apple Internal Keyboard / Trackpad
Thunderbolt Information: ℹ️
Apple Inc. thunderbolt_bus
Gatekeeper: ℹ️
Mac App Store and identified developers
Adware: ℹ️
Geneio [Adware! - Remove]
Kernel Extensions: ℹ️
/Library/Extensions
[loaded] com.globaldelight.driver.BoomDevice (1.3 - SDK 10.9) [Click for support]
Launch Agents: ℹ️
[loaded] com.google.keystone.agent.plist [Click for support]
[loaded] com.oracle.java.Java-Updater.plist [Click for support]
[loaded] org.glimmerblocker.updater.plist [Click for support]
Launch Daemons: ℹ️
[loaded] com.adobe.fpsaud.plist [Click for support]
[loaded] com.google.keystone.daemon.plist [Click for support]
[loaded] com.microsoft.office.licensing.helper.plist [Click for support]
[loaded] com.oracle.java.Helper-Tool.plist [Click for support]
[loaded] com.oracle.java.JavaUpdateHelper.plist [Click for support]
[running] org.glimmerblocker.proxy.plist [Click for support]
[loaded] pt.sapo.mac.cloudpt.injector.plist [Click for support]
User Launch Agents: ℹ️
[loaded] com.genieo.completer.ltvbit.plist [Adware! - Remove]
[failed] com.moeppfdpoohhdcaefbfpmabjipnohiif.updater.plist [Click for support] [Click for details]
[running] com.spotify.webhelper.plist [Click for support]
User Login Items: ℹ️
Spotify Application Hidden (/Applications/Spotify.app)
Internet Plug-ins: ℹ️
FlashPlayer-10.6: Version: 17.0.0.134 - SDK 10.6 [Click for support]
QuickTime Plugin: Version: 7.7.3
Flash Player: Version: 17.0.0.134 - SDK 10.6 [Click for support]
Default Browser: Version: 600 - SDK 10.10
o1dbrowserplugin: Version: 5.41.0.0 - SDK 10.8 [Click for support]
SharePointBrowserPlugin: Version: 14.0.0 [Click for support]
googletalkbrowserplugin: Version: 5.41.0.0 - SDK 10.8 [Click for support]
Silverlight: Version: 5.1.30317.0 - SDK 10.6 [Click for support]
JavaAppletPlugin: Version: Java 8 Update 31 Check version
Safari Extensions: ℹ️
YouTube5
3rd Party Preference Panes: ℹ️
Flash Player [Click for support]
GlimmerBlocker [Click for support]
Java [Click for support]
Perian [Click for support]
Tuxera NTFS [Click for support]
Time Machine: ℹ️
Skip System Files: NO
Mobile backups: OFF
Auto backup: NO - Auto backup turned off
Volumes being backed up:
Macintosh HD: Disk size: 498.88 GB Disk used: 124.67 GB
Destinations:
TOSHIBA EXT [Local]
Total size: 0 B
Total number of backups: 0
Oldest backup: -
Last backup: -
Size of backup disk: Too small
Backup size 0 B < (Disk used 124.67 GB X 3)
Top Processes by CPU: ℹ️
4% WindowServer
0% sysmond
0% ps
0% AppleSpell
0% fontd
Top Processes by Memory: ℹ️
241 MB thunderbird
172 MB Safari
155 MB com.apple.WebKit.WebContent
137 MB mds_stores
86 MB Finder
Virtual Memory Information: ℹ️
10.77 GB Free RAM
4.54 GB Active RAM
660 MB Inactive RAM
1.21 GB Wired RAM
1.50 GB Page-ins
0 B Page-outs
Diagnostics Information: ℹ️
Apr 13, 2015, 01:48:48 PM Self test - passed
Apr 10, 2015, 03:27:17 PM /Users/[redacted]/Library/Logs/DiagnosticReports/com.apple.WebKit.Networking_20 15-04-10-152717_[redacted].crash